I'm sure I've moaned about this before, but...
I can update my display drivers without needing to reboot my laptop, so why the fuck does Apple think I need to reboot to upgrade a fucking MP3 player?
Asshats.
It's some cock or other about restarting services I think. I'm sure that the installation is completed during the reboot.
If you ask Apple they'll probably blame Microsoft.
Also; iTunes 11 is gash.