A better/less deformed screen capture using google earth (again, had to use gimp):
It had no problems working. On the world view that screenshot was taken I got like 3 FPS though.. when I zoomed in more (to city level) it was much better (15-20 FPS) but still pretty slow. Also it could be my imagination but it seemed like google earth wasn't giving me a very high quality image (not rendering the textures at a high enough resolution for my zoom level... quite annoying. I don't remember the old version being like that.
Running multi card/monitor is nicer in XGL though as not only is window performance great but video overlay works on all three displays. I only get overlay on the primary screen on regular X using xv or vdpau output on regular X.