Comment 8 for bug 617994

I can confirm this for GTX 285 + maverick beta + binary nvidia driver.
Even launching htop causes the Xorg cpu-usage to peak to ~30% on an i7-920. I also noticed some much more serious spikes beyond 100%, which render the system almost unusable (mouse lags, audio playback hangs, etc.). These appear to occur more frequently when utilizing the card's 3d rendering capabilities (i.e. playing sauerbraten in my case).