alright, just bought a 1tb WD my book for 17" macbook pro. didn't look too closely and realised when i got home that it's usb2.0 and not firewire. is this a problem? does anyone actually run files (say, music or videos) off their HD (and seamlessly, at that?)? i imagine if i only use it for back up, i'd get away w/ usb, but if i wanted to do the former.. ? tia.