Comment 1 for bug 1039942

I believe that this problem *may* be related to the new window title and close button, which were added to Ubuntu as of 12.10. I noticed no lag before this plugin was added, but now it is quite often almost unusable. The issue may be the point at which the title is being drawn, as it quite often lags a split second after the animation is started and I can see the windows (sans titles). The animation only proceeds when the title appears.

Test:
Open four terminals in the same workspace. Click the terminal icon to spread the windows in that group, and note the point at which the lag occurs.