Comment 6 for bug 653851

The problem does not occur only with Nvidia chipsets but also with Intel Video (Intel GM45). The GUI is sooo slow it is unbearable. Here is one way to replicate the problem:
1. Click on Gnome Main Menu.
2. Start moving the pointer up and down over the menu entries.
3. In a few seconds Xorg will be consuming 50% of the CPU and gnome-panel the remaining 50%.

The problem is not limited to gnome-panel. It seems like any application that is updating the screen consumes processing time and at the same time causes the Xorg processing time to shoot up. No complex graphical operations are required for triggering the problem; opening a GTK menu in any application (thunderbird, gedit) and scrolling over the menu items causes excessive CPU utilization. The most notorious example was opening a gedit instance and scrolling through the File Menu causing gedit to consume 60% and Xorg consume 40% CPU. It is is also important to note that scrolling thorugh the Menu items is very slow.

The most annoying aspect of the general sluggishness in the interface is delays in text input. The characters that one is typing stop from appearing in the screen and one or two seconds later many characters appear at once,

The problem doesn't seem to be limited to Compiz or 3D effects either, because the sluggishness in scroling through the menus can even be observed after switching from Compiz to Metacity using the Compiz Fusion Applet.