This thread being an example.
I have noticed that there has been some concern regarding the GTX 260/280 and clock throttling in 2D/3D applications with the 180.4x drivers. This is normal. Earlier drivers had "Stuttering" problems due to the implementation not being bug free yet. So the feature was disabled in the 17x.xx drivers. It has however been reimplemented in the 180.4x drivers.
However the the clocks/voltages of your card will throttle up and down dependent on how the GPU is loaded. This is a GT200 card feature. Not a bug. It is entirely dependent on how loaded your GPU is. If your in a CPU limited enviroment the card will throttle down for better power/noise levels. If users are noticing stuttering with these drivers. Please post here and let me know. With software and settings.