Feature:
Everything you need for the road and much more.

Quality:
As a Panzer tank or an M3...

Value:
Excellent value if you compare it in the top range where it belongs (Apogee, Lynx, SSL, Prism, etc.)

Desirability:
I have one.

Sound:
The sound quality is german engineering, nothing less. The converters are AKM AK4620A codecs, state of the art in digital audio conversion. No coloring in the mid frequencies compared to Apogee. The drivers are very reliable for mac and the "total mix" is an amazing tool. The pre-amps are a bite digital sounding so if you want to record something like a voice or an acoustic guitar I recommend you to use a dedicated analog pre-amp. I don´t give it the 10 points in sound because I have heard the Lynx Aurora and thats about as good as it gets.

Ease of Use:
Plug and play, despite the bible that comes as manual.

Support:
No problems yet.

Overall:
Nothing better for the road or even the studio. Pro from tip to end.

Feature:
Most of the stuff is controlled only via software. This isn't a problem with me as I have external pres and a separate volume for my monitors. HOWEVER, it has basically every other feature you could ever want.

Quality:
THIS is why I like the product. It is THE best quality in every respect for this type of unit (2 mic, 6 line, adat, half rack types). EVERYTHING is top notch.... MADE IN GERMANY by the way (like neumann, sennheiser, BMW, and anything else worth having) so it's really sturdy. The clock is high-end, the ad/da is better than motu (not quite as good as Apogee) and blows everything else (at least on this website, except for the fireface 800 of course) out of the water. It is really fast too by the way - it has the lowest latencies of any comparable firewire interface, and is almost PCI-like. Excellent drivers and software control - no gimmicks and fancy-shmancy stuff, just plain, powerful, and professional.

Value:
Very expensive for the features.... but you get what you pay for. You're getting quality over quantity in this unit. If you want more I/O, just buy another pre strip like I did (despite my bad experiences with the two Firestudios I tried, the digimax fs actually worked out great!).

Desirability:
For its size it's cool/retro looking.

Sound:
This thing sounds so awesome and clean.... it's almost like it's turned up louder but it's not. Before this, I went through two Presonus Firestudios and couldn't stand the digital noise and crappy D to A. It sounds a little better than my previous card, the EMU 1820m, as well.

Ease of Use:
Very powerful, and thus a little confusing. The owner's manual is like a novel. For a geek like me, it's awesome, but I dunno about the layperson.

Support:
I haven't had any problems, but they have been releasing drivers (both firmware and software) pretty consistently, and I'd say that counts for something. As I said before, the manual is VERY in depth and could be used as a textbook pretty much.

Overall:
It'd be nice to have an easier time with the headphone volume control... but, I'm sticking with this for a while :)

Feature:
Its really portable. Everything is controlled through the software which I really don't mind. It is possible to link the left and right faders in the software, so that you can control the overall output/monitor volum through a rotary knob at the front of the device, and its possible to assign a midi controller to the faders for more hands on control.

Quality:
Really well built device. Looks professional and everything works perfectly.

Value:
Best thing you can get for a 1000 grand. Great converters, really good drivers for the pc and the mac. If your not looking for a portable device you should get the Fireface 800, which has more I/O's and more hands on control.

Sound:
Really good sound quality! Haven't used the preamps too much yet but they have done the job ok. If you are serious about vocal/instrument recording I'd get a dedicated preamp(this goes for any audio interface really, not just the fireface400.) On the AD DA side I couldn't hear any difference between this one and the fireface 800. I think the preamps are alittle bit better on the fireface 800, but not by much so it really doesn't matter. The only reason to get the ff800 must be the extra I/O etc.

Ease of Use:
Must say, I did have some problems installing the drivers. (In Vista mind you). Everytime I tried to install the newest drivers, my pc(Again, Duh!) would give me a nasty bluescreen. But then I tried a little older driver, from like 2 or 3 updates ago, and everything just worked! I can work with 64 or 48 samples without any problems. It works perfectly in Vista(At least for me), XP and on the mac.

Support:
They answer emails quickly and they have a great forum where you can get help or answers quickly.

Overall:
Really satisfied with the ff400. As I said, can't hear any difference between the ff400 and the ff800. I only bought the ff400 because I needed a portable FireWire soundcard. I had already tried and used the fireface 800 in a studio and really liked the sound.