We had vista installed on one of the machines and we didn't booted the machine for at least a few weeks. Once we did we noticed that it takes really long to boot the system, approximately three times longer than it usually takes.
Once you boot the system Vista wants to update everything and still prevents you to do your work. After 10 critical updates that happened in this week it wants you to reboot.
The same machine had XP installed and it didn't needed so much time to boot, so that is the surprising part but XP naturally wanted its piece of updates as well and a reboot.
We don't know if this is an isolated case but it certainly made us wonder. After that vista update and reboot delay the system behaves like it use to, boots fast and works well. Still after this delay it takes Vista an average of 50 seconds to fully booth and this sounds like a lot to us for a Quad core FX 74 machine with 4 GB of memory.