I never bother to uninstall, reboot, then install, reboot. Figgure their installer should uninstall old stuff like it's supposed to. Hit the installer, reboot, done.
You are just begging
for trouble doing that ZzeusS. Although I agree that their installer should UNinstall previous drivers, you really should reboot in between, otherwise you're not getting rid of the registry keys currently loaded into memory...
As for the new drivers, I'm still running the 3.6, which seems to be the only one I could find that's been hassle free with any games. As long as I don't run into any problems, I'll just stick with them. I still ran the 27.42 Detonators when Nvidia was releasing the 44.03s