@Makeshift... I've got the 18i6 but it is basically the same unit with a few different routing options (more ins, less outs, no loopback feature). The only thing I can think of to warn anyone about is the fact it isn't a super low latency devices like the Roland or MOTU boxes which supposedly get around 2ms roundtrip. The lowest I've gotten my roundtrip latency on it's fastest setting is around 7ms which is definitely not audible at all. That's what I set it to for tracking and stuff but I turn the buffer up a little when mixing to avoid dropouts and quirkiness (usually I'm getting about 12ms roundtrip at that setting which is again not audible at all). So really it isn't a problem at all if you have a decent computer that can handle those lower settings. I'm running an i7 2600k with 16GB RAM on Win7 just FYI.
The things I like:
Great sounding pres and high Z
Monitor and headphone knobs so you don't need another unit to control levels
The box is made of steel and the connections are solid
Uses a power adapter so it doesn't drain system power through the USB link
Pretty easy to use
Comes with some fancy Focusrite plug ins and mine came with Ableton Lite and Novation Basstation (IDK if they still ship with those last two)
Works like a champ and just sounds good
Their service is really good
I don't have this particular function but the 8i6 has a loopback feature so you can record stuff directly from other applications like a web browser without and physical cabling which is cool.
Note: I do not work for Focusrite. I think I have to start saying that because of how often I blather on about these units but really I just think it's a really good piece of gear for a lot less than other similar units.
Cheers.