As I am still a bit of a noob, don't expect everything I say to be absolutely, 100% correct. I ordered the HF5's on Amazon for 99 a while back, and they arrived just last week.
Design:
Wonderfully classy and subtle design. Too many headphones out there are either boring and ugly, or garish and vulgar. The Hf's are fortunately neither of those. Looks great, but you won't see much of it anyway when they're in your ears.
Fit and Finish:
Top notch, as one would expect from Etymotic. They've spray painted the body with a matte-type finish, and it feels really, really nice. Cable is kevlar reinforced (or so I've heard) and feels really durable. For extra peace of mind, Etymotic does have a two year warranty with these, so no worries there.
Comfort:
Because of the deep form-factor, these do take some getting used to. I started using the small triple-flanges, and they hurt, so I moved to the larger ones. They were ok, but started causing itches 30 minutes in. I looked past both foamies, as multiple reviews told me they wouldn't last for long. So i went back to the small tri-flanges, used them for a while, and gradually, they started to fit better. I can now wear them for a few hours at a time without any discomfort.
Isolation:
Etymotic rates them as 35-42db, and I have no doubt about this. Annoying parents, flight attendants, engine noises, subways, everything was cancelled out. Amazing isolation. A quick word of warning: Don't use these when in busy traffic; if a bus is coming through, and you're wearing these, chances are, you WILL get run over.
Accessories:
They came with 4 different types of tips (2 sizes of tri-flange, Glider, and large foamies), instructions and stuff, a nice, pleather pouch, and some extra replacement filters and the tool that is used to replace them. I was fairly pleased with the accessories that came with these.
Microphonics:
With the shirt clip on, I didn't feel anything. Without the shirt clip, the microphonics were noticable, but nothing too annoying.
Sound:
The most important factor of a great headphone, and fortunately, these surpassed my expectations, by a LOT. (Side note: if the fit isn't airtight, sound quality is ruined. It becomes all highs, and nothing else.)
Bass:
Since I was coming from Dre's POS, I was in for a shock. Used to muddy and bloated low-ends, imagine my feelings when I was greeted with a tight, precise, and extremely cohesive bass with relatively good extension and impact. Though it is true that the quantity of bass in this earphone doesn't match some dynamic driver-IEM, I can say that the Hf5's bass response is very well articulated and detailed. Extremely accurate or neutral is what I would describe the bass as. Bass bleed was nonexistent.
Mids:
Vocals came through with ultimate intelligibility, and were super clean and crisp. Singers did tend to sound a bit "soulless", with an inclination to sound technically perfect, but with a hint of coldness. The detail retrieval and utter transparency of these earphones simply stagger me. Again with the bass, the mids on the Hf5's blew me away with it's absolute accuracy and control.
Highs:
As many others have said, the highs on these depends on the bit rate or source. Throw in some 128kpbs mp3's and the highs will sound sibiliant and harsh. Any compression flaws or unnecessary artifacts will be heard loud and clear. However, with well-mastered, high-bit rate songs, the highs on the Hf5's start to come good. Every cymbal crash, hi-hat and guitar solo came through with an utter sense of neutrality and cohesion. If you're used to a more warm and laid-back treble, the Etymotics will re-educate you.
Soundstage/imaging/instrument seperation:
Soundstage is wide, but has only average depth. The good thing is that this presentation suits their natural and extremely cohesive sound signature. A large, Shure-like soundstage would be of no benefit to the Hf's. As such, the Hf's don't have quite a sonically three dimensional sound, the sort you would get from a high-end Westone or Shure. Instrument seperation, on the other hand, is second-to-none. Every single instrument and beat, could be clearly picked out, as well as differences between fore/background instruments. Fantastic stuff. What I like about this earphone is that it combines the "fun" and more musical sound of something like a Monster Turbine, and the exquisite detail and analytical sound that you would normally get from a BA IEM. Like most others, I would call the sound signature of the Hf5 cold, and occasionally bright (though that depends on the source).
Value:
For 99, it's an absolute steal. For 199, it would still be tremendously good value, given it's utterly brilliant sound and isolation. Even if they were 299, I would probably still fork out the money for these.
Conclusion:
This IEM has everything I would expect a brilliant IEM to possess: Clear, detailed sound; remarkable isolation; great build and finish; good accessories, and ultimate value. Etymotic has clearly put a lot of work into this headphone, and it shows.
(I'll try to post pics when I can)