Here's a novel use of Xbench, akin to using "Skin So Soft" as a greenie bug repellant on the New Jersey shore: Use Xbench to fix screen burn-in.
I was away for winter break, and my iMac froze shortly after I left, with the Flurry screensaver running. It froze for a month, and burned a swirl into the upper middle of my iMac screen. I normally have a solid blue desktop; it looked after this like a piece of blue cardboard that had gotten bent, and was a deeper blue along the crease. This persisted for days.
Does your head ever make you want to scratch it from the inside? I felt this way about my iMac display, no amount of pressure from the outside would help, what was needed was some serious scratching from the inside. So I downloaded Xbench, ran the Quartz Graphics Test, and quickly moved the window to the location of my screen trouble. I repeated this perhaps a dozen times, and I can no longer see any trace of the problem.
This was a lucky guess, what little I know about displays doesn't entirely agree with a prediction that this would work, but I didn't see how the experiment would hurt. With a tiny change to their code, Xbench could offer the option of full-screen looping your Quartz Graphics Test, as a screen doctor for other displays in worse shape. I proposed this to them; chime in if you like.
[robg adds: I don't know which model of iMac was involved in this incident, and none of our LCD-equipped Macs have a burn-in issue, so I can't test this one.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090123111428872