Mine is at 300 when in Windows, goes to 625 (current OC) when I am playing a game. I noticed that it does drop to 400 when in the menus or loading screens, but I have not seen any slow-downs in game (yet)
So far I have only played AoC, ME, and Crysis, using the 177.41 drivers.
I keep the fan on "Auto" and haven't noticed any temps over 75C ( full load)
I'm monitoring the above with the EVGA Precision applet on my G15 keyboard LCD, it's great for watching real-time changes in game