Guess I was actually one of the fortunate ones in that other than PD9 I haven't had any other errors with respect to the 280.29 driver.
When I got home I ran the DXDIAG's then downloaded and ran the four "cleaner" utils for PD9 and associated programs, then reinstalled PD9 and the Content Pack. So far it's more stable - it hasn't crashed yet - but there are a couple of odd behaviors with respect to maximizing the screen that I don't like, and general lack of responsiveness that I would not expect from a 64-bit native program in a project utilizing just 1/20th of stated maximum streams.
But, given the apparent issues with the Nvidia driver, I'll hold that opinion until the next driver release and just see how well I make it through my next project.
Thanks for weighing in, folks!