GE was buggy as hell for a long time. The dev's have been hard at work and I have to say that it is not just a "keep my drivers up-to-date" program but turning into a really cool tool. Early on GE was the cause of many graphic issues, especially on driver updates. I was forced to completely wipe all NVidia software from my machine then re-install with the latest to get things going correctly again. Kudos to NVidia on continuous updates.
Regarding clean installs, you should ALWAYS clean install drivers. It is a DRIVER, not a program. If you do not, you run the risk of potential issues. The only thing I wish was added would be the ability to backup the individual game profiles from the NVidia control panel under Manage 3D settings. There has always been an option to Restore defaults but having the ability to back that up locally or to your GE account on a game by game basis would be great. That way, a clean install would replace the drivers correctly and a simple "settings" restore of games would put all of it back. This would save quite a bit of time on the reloading of drivers. But if the only "issue", which is more of a hindrance, is for me to re-tweak my games profiles, I'm good with that. I wouldn't complain too much about NVidia drivers. If you think they are bad, switch over to Radeon and give those a shot...