For what it is worth, my Exposé performance was terrible at first, which I attributed to running a number (4) of extra displays on two Radeon 7000 PCI cards, in addition to my primary video on the AGP bus. Since Quartz Extreme isn't supported on these screens, Exposé was very slow, nothing like the smooth experience we've seen in demos.
I went ahead and threw caution to the wind and reinstalled PCI Extreme, which successfully enable QE on PCI cards in Jaguar, and was pleasantly surprised to find that it appears to function perfectly under Panther. Exposé performance is vastly improved, as are many other functions. Note that some users find that enabling QE on PCI cards can cause other performance issues, though I've never personally had this problem myself
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031025182652488