Damn, the first one is a performance update and the other is a reliability update so they look important. However, the reliability update could simply be related to unsigned drivers.
The unsigned driver policy is about the only thing keeping me from pulling the trigger on x64 Vista. What I don't like is that it shuts out hobbyist drivers, such as for game controllers made for consoles (which are much better than PC game controllers IMHO). I know MS has a driver for the 360 controller, but you can't configure the buttons/pad/sticks like with XBCD.