I'm thinking of buying one, since it really seems to be the perfect audio interface for a home studio. I'm just going to wait a little, because I've heard on some forums that they are not compatible with OS X Tiger.
Well I got a M-Audio Firewire Solo and it works great.
It works great with Metro 6.3.1.1 and has worked on everthing
on my Mac Mini. I am using Tiger 10.4.2
It's well worth the money. For midi I use a M-Audio 49E keyboard
controller, because it was cheap in price but not in performance.