Hey ekrimen
I use a USB 2.0 card in my Pismo. Works Great. But Isn't as Fast as FireWire. I've times Transfers from Internal Drive to and External Drive, with both fireWire and USB 2.0, and FireWire is always 5-7sec Faster for some reason. To Bad USB 2.0 doesn't Boot with OS X 10.3.8... USB 2.0 External Drives are a lot cheaper...
Great Times!!!
Brad