3danalyze is useful for testing purposes. Interestingly enough, using 3danalyze can let you run demos from Ati, Nvida, and Matrox on whatever card you have as long as it has similar capabilites.
Ati's Ruby demo runs fairly well using 3danalyze on my 6800 ultra. Matrox's Reef demo runs pretty damn amazing.
YOu can also use 3danalyze to trick applications into thinking your running a different video card. Of course it doesn't work too well if your card is much weaker than the card your trying to trick the app with.
I also tried it with Sonic Adventure 2 in Chankast and nothing is different. Still a few glitches in the first level crashing soon afterwards.