I think this weekend I'll reinstall Leopard. I'm sick of system hangs, beachballing, poor Flash video playback, general unresponsiveness, file type issues and associated apps (.rar vs .cbr, .zip vs .cbz), app crashing (Safari, TweetDeck, iTunes 9), bizzare shuffling between QTX and Quicktime 7.
I've posted about each of these problems on the forum ever since I installed Snow Leopard, and it seems clear that this OS is a real mixed bag. Some people have no problems at all and everything has the performance boost promised. Some people have no problems but no appreciable change. Some people have bugs and problems (like me) that make SL hard to use. Some people have completely dead machines (kernel panics, machines that won't shut down or start up).
I can't work out what the common thread is - my machine isn't that old (late 2007 alu iMac) and isn't specced that badly (4GB RAM, 500GB HDD, 2.4 GHz proc), yet I've got major issues with the OS. I've done a clean install before anyone asks!