So a couple of friends loaned me the E12 a month or two back and I have been listening them on various rigs and familiarising with them over a while, I'm not that experienced in the portable realm but will do my best to give you a clear picture of the sound(hopefully).
 
Design:
With the design, I find the switches mostly a pain in the arse to use because they are recessed when I use the amp with different headphones, like my hard to drive AKG 240DFs and say the more sensitive IM-70 from Audio Technica. This problem is solved in the E12DIY which sports a gain flick toggle switch at the front panel at the price of giving up all the other features of the regular E12. I really like the knobs on the amps as they still do no feel very loose after the two months I have them and they are also less prone to accidental adjustments due to their design.
 
Sound:
Without ado, I felt the Mont Blanc was pretty win(and maybe their only win product in my book) so far, having owned the E11, its a huge step up in sound and direction of Fiio. The soundstage is pretty large compared to the Project Iona I had at the point of review. Comparing the Project Iona, O2 and E12 side by side, the E12 comes of as the warmest sounding of the bunch(though they all measure flat) and also the most technically competent of the bunch. Bass wise, the E12 tops out have a more defined bass body than the O2 which sounded somewhat mushy in comparison. As it has a good amount of power, it swings between volume levels without feeling compressed and strained compared to the Objective 2 which was flat(like dynamically flat) in comparison into harder loads(it still holds true even for easier loads though). The one quibble I have is the lack of synergy/drive with a picky headphone like the HD800, which is probably due to the choice of opamp(OPA1611 iirc) used. It sounded harsh and dry into the HD800 whereas my receiver though noisier, drives the HD800 effortlessly(I noticed the same in other big amps of course) so don't be too tempted to use this into replacing a proper desktop amp. Into the AKG240DF though, I'm simply happy with the combination.
 
As for the switches, I found the gain to provide a good balance between the headphones(and the feel in-ears) I use. The bass switch is pretty good, boosting the low end of some headphones in a good way without obscuring the mids. For me, the crossfeed though a boon for some was frankly just junk for me, I think I would stick to software or higher end implementations of crossfeed. For the purist though, these added features to an extend kinda harm the sound and is the cause of the hiss in the E12, how I know? Thats because I have the E12DIY which removes all these features and changes the gain switch to a little toggle switch, I love it. For the purist, get your hands on the E12DIY especially if you have sensitive IEMs
 
Right now, I'm using the E12s as one of my reference amps given my heavily budgeted situation and will update impressions on fitting in some of the better (newer) opamps into the E12DIY and see how it goes. Other then that for the regular headphone users(portable headphones or studio cans) I heartily recommend the E12 and for those more discerning ones with sensitive cans and IEMs, I recommend the E12DIY even if you don't "DIY".
 
Associated Equipment: Creative SB1240, Stoner Acoustics UD110MK2, Ipod4g w Accudio, HD800 Rabid Dawg, AKG240DF, Audio Technica IM-70

Decided to write this review to hopefully answer any queries anyone may have. 
 
The creative X-fi back last year, was one of the best DACs out there with very good value for its performance, conducting some tests with RMAA, I found that it has good 18 bit performance and true 16 bit performance that was pretty much unmatched by any DACs at that price back then (there is now the ODAC). Still, its a pretty clean sounding dac, and less grainy than both the E7 and E10(I borrowed them). Overall it is a pretty good dac that has good technical performance as expected of a DAC designed with proper tools. 
 
However, with headphones, it does a terrible job, I think it is a problem with output impedance like many before me has mentioned. Despite using a JRC4556, it fails with balanced armatures but fairs fairly well with regular headphones but is less capable than a E7 that I tried once. With my TF10, the X-fi HD is muddy yet harsh at the same time.  The headphone output clips when using Isone with my previous ATH-M50s, indicating that even 32ohm dynamic driver headphones bring it uncomfortably close to clipping.
 
Another issue that users experienced is the lack of 44.1khz input which is utterly ridiculous and a huge disadvantage compared to the competition. I myself resample all my sources to 24/96 so it isn't too bad. Not resampling increases distortion quite a lot. But for videos, I find that it is of little issue as audio in videos I watch is typically 48khz which is within the sweet spot for the X-fi HD
 
Now on to its drivers, Creative does have its bloatware but has so far caused no particular issues with playback for me, I'm using Jriver Media Center's Wasapi Event style for all my music playback. Its optical inputs and outputs require external drivers which is a big minus when I want to use this with my cd player for instance, I will need to have a computer running to accept optical in. 
 
Overall, I find that despite the release of new DACs like the E10, I find the X-fi HD quite competitive for the price as a DAC only device, since the E10 only barely makes it pass CD quality in 24 bit mode whereas the X-fi HD is fully 16 bit capable(-94db) and is capable of 18bit operation which is a lot of headroom for adding DSPs. Now with the ODAC though, it is a pretty outdated component and I can't really recommend it to anyone for playback only. The good thing is that the analog inputs is decent(not extremely fantastic) so those hoping for a cheap way of converting their vinyls to digital copies have a solution there.
 
Those seeking a DAC and headamp combo should consider the E17, E10 or E7 which are better than the X-fi HD for what they do with headphones. 
 
Equipment used for review: in my signature
Player: Jriver Media Center WASAPI Event Style

Introduction and initial impressions:
Bought them over a month or 2 back for the lols and now they are my regular for my daily commute. I have used them with a fairly wide variety of audio devices, Iphone 3g(Objective 2,FiiO E6 and E11), Sony Z series(briefly), Ipod touch 4g, Sony BDP-S380(w O2), Creative X-Fi HD(O2). Initially, I thought the TF10s were terrible, sound felt unnatural straight from the Idevices and it was too noisy with the E11. Hence, this review will discuss the TF10s mainly with the O2, Fiio E6 and Sony Z series.
 
Accessories:
The TF10s from Amazon comes in a super nice packaging and a fair bit of accessories. Flight attenuator for reducing audio system noise, wax cleaner, a nice gold 1/4" jack and extension cord. To boot, it also comes with a pair of comply tips.
 
Comfort:
Fit is hard to find but if you get it, it is ridiculously comfortable and reassuring fit. The stock silicone medium tips are my main tips now.
 
Cable:
I have to mention this, the cable sucks with memory behavior, so just get a Fiio UE cable replacement if you want something cheap. For others there is also Null audio cables which are very nice too. At this point I'm still waiting for my cable(on preorder)
 
Sound:
 
Separation: Very good instrumental separation which is on the ER-4S level. Only issue is the it seems very dependent on amp. The E6 and O2 are some of the cheapest options which provide this for me.
 
Isolation: If I'm not wrong the it is rated 26 SNR for isolation and I used the TF10s as ear protection in noisy situations and work. It works very well at blocking out noise, while looking cool during repairs
 
Soundstage: I see no point in this but for a IEM, the TF10s have a wide soundstage.
 
Bass: Good bass reproduction with a lot less bloat than my previous M50s while being having a good quantity compare with the lack of bass of the ER-4S.
 
Mids: Good smooth and coherent mids, great for female vocals. I found the mids very slightly recessed
but its a non issue for the smooth smooth vocals.
 
Treble: Having heard so much hype on Head-fi and my friend who uses it with his Ipod. I was unimpressed with the mid- high treble on the TF10 with the E6 and E11(with attenuator). Its just barely there. Some songs as a result, seem to lack the high end for me. Its like the polar opposite with the ER-4S. Only with the O2 I managed to achieve a sufficiently good high end from the TF10s. The E6 does well if not stellar performance in treble.
 
Tonal balance; Overall neutral but with slight recess in the mids(which is really really small) and virtually no treble unless you have a good amp to pair with it. A Pico Slim would be a good too.
 
Verdict: Would I recommend this to someone new to audio? Maybe not without a fairly decent amp at least. Its highly recommended if you seek a more neutral sound(based on my Edifier R2000T, ER-4S and DT880) but still keep that bass. It's totally value for the price compared to ER-4S and is a keeper. I'm suprised that it did as well as it did on HF(price?) as I found it pretty source picky with lack of treble on a improperly matched amp(and straight out of the every popular Idevices).
 
 
 
 
 

So finally I gave them up for an upgrade. Now to write what I think of them.
 
Build and Design: 
I think these are some of MOST solidly built cans I seen comparing to the ATH-SQ5 which was my previous cans and other cans like DT 235, Shure 440 which would be important to say DJs. Its very portable to store away too with its swivel cups. There are days which I would just chuck it in my bag and safe to say when I sold it away, it was still in very good condition considering my heavy usage pattern(mobile warrior).
 
Sound:
I did not do a review back when I got it because I did not have a high up there reference but now that I have an idea of how these cans are.
 
High.
Good treble detail but slightly forgiving. The now similarly priced Shure 840s will give you better highs though.
 
Mids
Despite having the white box ones, I still find myself pushing the volume up to hear those vocals, so the mids are still kind of recessed. Guitar tracks sound a little flat on some songs but otherwise it is pretty minor.
 
Bass
Oh man, this has all the bass I need, sometimes I think a little too much but maybe that is because of bass bloat? 
 
Overall: 
Sound quality wise I compared these to the DT770PRO  and I'm pretty sure its just a sidestep, with the 770 needing an amp to drive it. Vocals sound a little distant compared to the DT880 and ER-4S both which are somewhat a reference to me. Soundstage is very closed though. Switching from my monitors (R2000T) or my NAD speaker system to the M50 would give me headaches. I recommend using crossfeeding like Isone Pro or Redline Monitor with them.  
 
I absolutely recommend looking into the second hand market as these can go pretty cheap and in great condition. 
 
 
So in the end do I recommend these? Yes, but mostly for DJs, people entering from consumer-fi and road warriors. I think the alternative, Shure 840s, DT770s are better cans then the M50. 
 
 
 

Like ^ I bought the E6 amp on a whim to try out, it kinda came in a bundle with the Feels Pro 900 and Hippo Boom from Jaben. To tell the truth, the bundled in-ears did not synergise with the amp at all, details were lacking and the sound was pretty muddy to me even when i set it flat. It does better with headphones of course and is able to make my m50's sound better. It made the soundstage more natural and wider than that of my Iphone(duh anythings better than that :3).
 
However it is not as detailed as the E11 which I bought before the E6. Also, while the EQ2 options and EQ3 are pretty nice EQ functions of the amp, EQ1 itself was down right terrible, it was muddy and any vocals where pretty much drowned out unlike the E11's bass EQ. It could be my bias since I do not have drum instrumentals and rock, EQ1 could have probably done better. 
 
Overall I think the E6 is a good little portable amp, great little design, average amping with some detail loss. Good to use with the more affordable side of headphones where they tend to be more bass overkill. Probably would have thought better of it if I ever used the E7 or E5 amps. 
 
Just to let peeps know
EQ1 bass boost
EQ2 +db(forgot how much)
EQ3 -3db