Just to let you all know that I had awful problems with my macbook pro Core2 Duo (the last one before unibody). The firewire chip in it doesn't play well with FF400, and the USB ports are underpowered. Had terrible stuttering in cubase. I tried the firewire extender, but this made no difference.

Anyway I have just bought a new windows 7 pc and the same ff400 works flawlessly down to 1.5ms.

Just thought I'd share my experience