Disclaimer: I've got my RE272 as a review sample for free.

There are more pros and cons in my full review, like
 
Quote:

- RE272 bass accuracy is excellent, but I like to have it perfect.
- Soundstage size is good for IEM, but I like to have more.

Click to expand...

 
But this is just a nitpicking, and I do not consider this as a real "negative aspects" (this is how cons are defined here in Reviews section). I rather call this "wishes".
 
Conclusion: I prefer RE272 over any IEM I tried. 
 
Tried, in order of preference (not just SQ): RE262, RE252, RE0, ER-4P/S, MTPC, E500 (SE535), RE-Zero, CK10, SA6, ER-6i, E4c (wow, this is ancient!), UM2, some more. Note: order may change depending on the source.
 
Similarity: RE272 sounds like ER-4P reincarnated into dynamic driver version. And it turns out to be a step up over ER-4P, rather than a side steps presented by former HiFiMan models.
 
More in my RE272 review and comparisons to ER-4P, HD650, ATH-CK10, IE8.

Pros comments
Excellent tips and their choice: Tips are critical for IEMs sound and comfort and MTPC has the excellent stock tips. From numerous tips I tried, MTPC rubber tips are the most comfortable to wear and convenient to insert. The previous favorites were Sony hybrids, Shure E2c and Jays rubber tips. MTPC foam tips are also top-notch, in terms of sound, comfort and durability. Gel-filled tips look promising, but unfortunately do not fit my ears.
Plenty of accessories: cases, ear tips holder, shirt clip and so on.
 
Best uses
Portable Electronics
Travel
Delta-sigma budget DACs
 
Disclaimer
I was given this product as a gift in exchange for writing this review,
 
Conclusion first
From earphones I tried in $400 price range, MTPC is my favorite for use straight from mainstream DAPs, un-amped. MTPC strong and deep bass helps power-deficient portables to sound big, speakers-alike. Warm midrange makes digital sound livelier; highs are forgivable to MP3 artifacts. No need for deep insertion, ease of putting in and taking out make MTPC an excellent IEM for those “not so serious” audiophiles, who want both great sound and convenience.
 
Warning
With warmer source / amp, like multi-bit HM-602, MTPC yields in clarity and instruments separation to lean sounding competitors.
 
DETAILED REVIEW
 
MTPC bass is certainly emphasized but in a very wise manner: deeper is frequency – more is emphasis. This psychoacoustic trick works well with the headphones / earphones, because it partially compensates the loss of hearing sensitivity on lowest frequencies and absence of kinaesthetic perception of bass by human body. At the same time, such emphasis does not affect the midrange a lot (no “bass bleeding into midrange”). I like this, because:

• This fools the brain to “feel” the bass, giving the good body and scale to the sound. I agree with Monster when they call MTPC “In-Ear Speakers”.
•  This also helps to listen on lower, safer volumes or to block ambient noise.
• This lets to not wrestle with a perfect seal and deep uncomfortable fit.

 
Is MTPC an earphone for bass-head? This depends on a tips used; with some of the included tips bass becomes painful to me. With others it is just right until I increase the volume. On higher volumes bass becomes too much for me even with “bass-shy” tips. I appreciate this, because this forces me to listen on safer volumes. Bass extension, attack and overall quality are very good even on high volume.
 
Midrange is a bit warm and very slightly blurred by rich decay. Thankfully, this works for the good, smoothing out the harshness of digital sound coming from the ordinary DAPs.  Speed, details, clarity, instrument separation are just right for the task. I know some earphones which are better in these terms. But they sound harsher with mainstream DAPs, MP3 records and budgetary delta-sigma DACs. Here MTPC keeps a nice balance of speed and smoothness. Unfortunately, warmer sources (say HM-602) break this balance, instruments separation and details are suffered.
 
Highs are nothing to complain about, their quantity is just right and quality is decent. With my “sibilance test” records MTPC produces nice results – the sibilance was low, while highs were not subdued.
 
Aside of deep bass emphasis, overall frequency response is pretty even. When listening loud, some may complain that mids are recessed comparing to strong bass. Well, do not listen loud, this is just harmful.
 
I listen to variety of music and I like MTPC genres versatility. There are just few genres where MTPC yields to some mid-centric competitors. These are vocals and small acoustic bands. Other genres, including (but not limited to) blues, rock, pop, trance and especially ambient are reproduced with excellence.
 
Sensitivity: MTPC plays great directly from a DAP, though good amp (say Corda Move) may further improve bass control and instruments separation. Lesser amps have no sense.
 
Is the “For serious audiophile” claim, placed on MTPC box, correct? Yes, for those of us who are not willing to give up convenience for sound quality. Those, who do not want to struggle with half-baked boutique DAPs or bulky DAP/amps combos. Those, who prefer a perfect usability and slim form-factor of mainstream DAPs, like Clip+ or iPod. Those who want putting in / taking out the earphones easily and does not want to bother with perfect seal. Those who do not want to chase for the better ear tips or ordering a custom tips just to get a satisfactory bass. To those people I can recommend MTPC heartily. Let me call them “not so serious audiophile”
 
Would I keep MTPC? No. My main source is HiFiMAN HM-602, which does not pair well with MTPC.  But I wish my final IEM (yet to decide) will have MTPC full-blown bass and speaker-alike effortless sound. Reviewing MTPC, I rediscovered the value of properly shaped bass response for the earphones. Thanks, Monster!
 

 
COMPARISONS
 
I tried / owned following mid-fi and hi-fi IEMs: RE0, RE-Zero, RE252, RE262, ER-6, ER-6i, ER-4P, ER-4S, E4c, E500 (same to SE530), UM2, UE 5 EB, SA6, ATH-CK10. I decided in favor of HiFIMAN RE262, so I compared MTPC to RE262 with some portable sources:

1. MP3 > Sansa Clip+: MTPC is the winner. RE262 is underamped – lean bass, dry mids, lack of speed.
2. MP3 > iPod 5^th Gen, iPhone 3G: the choice depends on music genres. For those who like various genres, like me, MTPC is safer bet due to the stronger bass and forgiving highs. RE262 is sometimes lean, sometimes sibilant.
3. MP3 > iPod 5^th Gen > LOD > Meier Corda Move: there is no clear winner or preference. MTPC may sound boomy, while RE262 may sound sibilant.  Otherwise both sound good, so “choose your destiny”.
4. FLAC > HiFiMAN HM-602: RE262 wins hands down.

 
MTPC is the best for MP3s, cold delta-sigma DACs and low-power sources – say un-amped mainstream MP3 players. The only IEM which can compete with MTPC in this field was Shure E500. I did not compare these directly, but I prefer MTPC basing on my memories. E500 is less comfort and convenient. It also has the feature I did not like – extensive macrodynamics. Listening to orchestra classic, I had to raise the volume for cellos solo, then crescendo came and I had to reduce the volume, otherwise it sounded deafening.
 
So I stayed with my RE262, but I am less satisfied with it after I tried MTPC. MTPC bass depth and weight are something I am missing now. And I am not sure if custom tips for RE262 will solve this issue. Well, head-fi is a journey, there are many things to try yet – upcoming models, high-end customs and so on. With regards to MTPC, I thank Monster for opportunity to try an outstanding IEM. MTPC took its place in my personal “IEMs hall of fame”, along with RE262 and ER-4P/S, being unbeatable in simple “MP3 > ordinary DAP > IEM” application.
 

Disclaimer: I received review sample from Sunrise Audio for free.
 
Sunrise SW-Xcape
 
I would compare Xcape to RE0 and RE-Zero, like most did here at head-fi. And I place a conslusion first:

Any day I will prefer Xcape to both RE0 and RE-Zero.

Why? See the quote from my review RE-Zero vs RE0 - SS vs tubes:
Quote:

Both belong to those rare dynamic earphones able to compete with armature IEMs in speed, clarity and resolution. Both are on a lean side of neutrality, I would like to have more bass, but I yet to find bassier $100 IEM with the same level of SQ.

Click to expand...

 
With XCape I finally have the satisfactory bass with subtle (if any) loss of other qualities. Yes, mids of RE0 and highs of RE-Zero are tad better. But I had to amp them to shine. Unamped, RE0 is slower and RE-Zero is dryer in comparison to Xcape. Add here that I do not use portable amps now and you will get a picture - Xcape is a clear winner to me.

Sound sig: Amped or not, Xcape is not inferior to REs. It rather suggests alternative sound signature with more body and fun at the expense of some very subtle details. This is what I prefer, so Xcape is better all-rounder to me. And it keeps this advantage either it is amped or not. When amped, Xcape also improves on SQ, like REs do, and keeps a parity.

Comfort: Xcape is a bit better in terms of fit to me. I prefer over-the-ear style with all of these three IEMs. Due to the bended strain reliefs and differently shaped shells, Xcape is more comfortable to me.

Are REs obsolete now? No. The final choice depends on your source and genres preference. If you prefer acoustic music and use amps, then I heartidly recommend RE0. For unamped listening of electronic music or movies, some may prefer RE-Zero. If you are unamped and listen to almost everything, like me - choose Xcape then. If you already have any of REs and it suits your needs well - keep it, the differences are subtle, all three IEMs mentioned here are pretty similar. If you do not like any of REs much, keep away from Xcape as well - it doesn't offer night-and-day difference. Basically, I may describe Xcape as a blend of RE0 warmth and RE-Zero sensitivity.

Drawbacks: I much prefer REs visual style, especially RE-Zero gunmetal color. Xcape looks cheap in comparison (though it is cheaper indeed). Included tips choice are also better with REs, though Xcape repays this by the included case.

 
As title said.
 
I love HM-602 DAC. It beats HDP, Sparrow, Pico DAC/Amp, D10. It does provide musical sound, which is closer to analog, namely to tapes / cassettes. It also does not give up to the DACs mentioned above in summary of technical terms. I mean specific SQ terms, taken by ears, not measurements.
 
I bear with HM-602 amp. It is good enough to not hassle with most of the portable amps. I compared it with Meier Move, which is one of the best portable amps I tried. Headphones were HD-650, RE262, KDE250, PortaGold and KSC-35km - last two are my deep modded Kosses. Music was various. Move was better in most cases, but not better enough to carry bigger brick around and to worry about batteries. HM-602 sometimes was passable, sometimes had excellent synergy, say with Kosses.
 
I like the resulting sound. This synergy with Kosses sounds like HiFiMan tried to reproduce 80's portable sound, say Walkman > PortaPros. Well, the mission complete and I respect the results. I grown up on this sound and I always feel myself comfortable with it. It is kinda "Back home, baby. Welcome back to 80s". I am still interested to climb higher on SQ, but HM-602 shows me the right direction now.
 
I can hardly tolerare HM-602 firmware. Using HM-602 buttons, it is really possible to develop UI same to or better than Sansa Clip UI, which is miles ahead.
 
I hate HM-602 informational support. I bought $80 Class 10 SD card just to learn it does not work. Customer support replied quickly - yes, it does not work, but Class 4 works. They knew this and they still did not added this info on to official product page at head-direct.com. It is a shame.
 
So, what is a summary? See my sig. If HM-602 is still there, then it is still a winner, despite its flaws. It presents one of the best combinations of SQ, portability and functionality up to date. It provides the best SQ among all the portable DAPs I tried, including all iPods, all Sansas, some Cowons, Sonys and HiSounds.
 
I respect what HiFiMan (Fang) does for our hobby. This product is another great long-awaited gear for head-fiers. Unfortunately, there are some major things to improve aside of sound quality. I hope my review will help Fang to make customer satisfaction even better. Some things, like public info on product incompatibilities, a very easy for vendor to improve. At the same time, they are critically important for customers.
 
 
Update Feb 20, 2011: I love it, it is incredibly great. It makes portable amps pointless and has a nice synergy with HD650. It is the best player I ever owned and the last I ever will part with...
... until it plays from my laptop USB. Unfortunately, it adds clicking noise. It requires a powered hub to play right. I yet to solve this with a customer support.
 
Update Sep 23, 2011:
It works well from USB with USB hub, even if no external power is used, just PC > Hub > HM-602. I found small hub and now can use USB with comfort. 
I prefer to add Meier Move to amp HM-602, when listening HD650. HM-602 amp is evidently colored, sometime this is for good (with RE272), sometime not (with HD650). Move is much better with HD650.

There are some who say HD650 demands for expensive amps. I disagree, HD650 is great with lesser sources/amps and excellent with higher gear. From Hi-Fi cans I tried (DT990, DT880, HD600, AD2000, AD1000PRM, W5000, D2000, K701), HD650 is less finicky to pair, while it is on top of this heap in terms of SQ. It is also moderatley priced for Hi-Fi can, half of those mentioned above are more expensive. Add that I bought mine barely used for $150, so it is a keeper for me.
 
Soundstage becomes bigger with better amps, like WooAudio 3 with upgraded tubes. Clamping force can be reduced, if you store HD650 with some spreader for headband. I recommend not to store it on a things like basketball, since you will flatten the earpads.