Well I should have listened to my own advice. I was getting various crashes in the client (usually after having tried to reshuffle my custom controls) so I figured I'd try the newest drivers.
First thing I noticed after install was all of the flashy Vista graphical flairs like button glows and drop shadows had now become pixelated noise instead of the smooth glows.
Then I noticed some flickering of the screen that would come rhythmically every 10-12 seconds or so. Then the screen started to fuzz up with graphic garbage like the cable was receiving interference from somewhere.
Tried a rollback: no dice.
Tried in Safe Mode to uninstall the newest drivers and reinstall the old drivers that had been functioning fine for well over a year: no dice.
Successive reboots just seemed to make the problem worse and worse.
Tried checking all of the cables, didn't make any difference. So I tried unseating and then re-seating the graphics card, and now I can't even get a video signal at all. All the fans come on, system is running, hard drive is running, I even hear the Vista tones as you get to the desktop, but my video system is apparently fried or my card is now dead.
Now I'm off to find a backup card that will work in my system.
Be careful.