It's always been the case for me, with the exception of one really old laptop drive that wouldn't have fit in the enclosure in the first place. You do have to use the double ended USB cable, as usb ports are speced at .5watts, and the drives pull 1 watt. Many computers will regulate these to prevent you from killing the motherboard, which is what leads to the working on some computers and not on others. Firewire ports provide the full watt the drive needs, AFAIK.

Matthew