Just wanted to chime in with a small success report. Using the stock nVidia drivers which come with the 10.8.2 update I was able to upgrade my MSI GTX 590 to an EVGA GTX 690 (that just came in 25 mins ago) just by switching GraphicsEnabler to "No" and dropping the NvClockX.kext. The card runs around 10°C cooler when idle and is far quieter. Very, very happy with it.