A number of my friends point to Android's laggy scrolling as the reason they wouldn't consider it over an iPhone. It'll be interesting to see if the hardware acceleration fixes this defect.
Edit: Maybe because I've always used launcher pro?
Opera Mobile (GPU accelerated), with a decent launcher, memory optimizations (V6 Supercharger, or a good Autokiller config), and Android will perform just as good as any other mobile OS. Unfortunately to get great performance Android needs to be rooted.