I've just been playing with this and it sounds great. Only thing is that there's some wierdness with the FireWire driver on some G5 machines. You have to download a new driver from Apple as part of an SDK which is not a very elegant solution.
Caused us a bunch of hassle trying to install it but we got there in the end.
if you dont install the driver, you can get a large recording delay which makes it totally useless for overdubbing or playing to a click etc.
Apparently, they dont have this problem on the PC