1. Some machines have trouble recognizing them for use in teh BIOS (usually solved by enableing USB keyboard support, i've never really had a problem with this one)
2. I have a Logitech keyboard and if I print, use my USB memory key or sync my PDA my keyboard goes into an infinite loop of disconnecting and re-connecting for some reason. It doesn't matter if it's plugged into the computer directly, plugged into the hub, or if it's just it and one of the other devices plugged direclty into the computer. It still does it. It doesn't have any problems with my USB sound card or my external HDD, go figure. Very anoying to say the least. Plugging it into the PS/2 port solves the problem though.