I installed the new NVidia driver today and observed the following:
With the Nvidia driver active, I cannot run OpenCL benchmarks, since I have both a GTX 580 and a GT120 card in my machine, and they don't play together well with the NVidia driver. With the Apple driver active, I can run all the OpenCL benchmarks and apps.
Scores in Furmark and Heaven are identical with the Apple driver and NVidia driver.
Based on these observations, I'm going back to the native Apple driver. It appears they got it right.