After reading the Andreas Gihr post about greater power consumption, I did a little test. Using Kubuntu KDE 4 I put the display at 60Hz and watched the GPU temperature drop 3°C. Put it back at 120Hz and the temp go up the same 3°C. But to me, this is expected. The GPU is working more to double the FPS of the KDE compositing. So is natural it getting hotter.