OK, this issue has annoyed me long enough. Time for some ranting.
I have a PC running Windows Vista. I have an iPod Shuffle, and I also have an iPhone. Now, the combination of these things is just terrible. Whenever I connect my iPhone or my iPod to my PC, I get the annoying message "This USB device can perform faster if you connect it to a Hi-Speed USB 2.0 port".
The only way I found that allows me to synchronize my iPhone or iPod, is by shutting down my PC, disconnecting my USB keyboard and mouse, connecting my iPhone or iPod, then booting my PC, and wait for iTunes to show up. When iTunes finally started (yes, iTunes is terribly slow on Windows*), I can connect my keyboard and mouse again. My iPhone or iPod will stay recognized as USB 2 until I reboot the machine with keyboard and mouse connected to my USB ports.
Now, when I connect my WD MyBook to ANY of my USB ports, I never get this warning, ever. This definitely proves that the problem is not caused by my PC or Windows, but rather by the iPhone and iPod.
Recently I found something about this on the Apple website, saying that I have to make sure that no USB 1.1 devices are connected to the same hub as the one you connect the iPod or iPhone to. Unfortunately I can't seem to find that page again, because the search function on the Apple website sucks. Besides, it's just another load of crap since my WD MyBook works fine on any of the USB ports available on my motherboard. Fix your USB implementation damnit!
Another annoyance is that sometimes, when I connect my iPhone or iPod, the thing gets recognized, then disconnects, over and over again. In case of the iPhone, this results in an error "iTunes could not connect to the iPhone because an unknown error occurred (0xE8000004 or 0xE8000001)", and the iPhone repeatedly making the sound it normally makes when you connect it to your PC. I really can't hear that damn sound anymore - heard it way too much.
So, my conclusion? Apple deliberately adds PC/Windows incompatibilities in their products, just so people would end up buying a Mac to sync their iDevice with... which is just utterly lame.
*PS: I have a PIV 3.06 HT with 1GB RAM. If that isn't enough for running iTunes, well ... What the heck ?