ok well i ordered a 320gb mybook with usb and firewire off ebay, but when i got it, it was a 500 gb one but with just usb. so i messaged the guy and asked him what went wrong. but im really starting to like the idea of the 500gb, so im wondering, is having only usb gona be slow? how much faster is firewire than usb? and this drive will be used for backups and possibly running files and apps off of.