I have a 2010 iMac 2.93 i7. I did an upgrade to Lion when it first came out and really have been underwhelmed since that time. Lots of beachballs, random weirdness with audio, and even an occasion hung computer now and then. I had hoped that subsequent patches would fix things, but it didn't. Recently the mail app started crashing frequently and Safari would hang for long periods of time. I tried all of the suggestions on permission repairs, etc. and nothing helped. I finally got fed up yesterday, backed up everything on an external hard drive, nuked the internal drive and loaded clean. It took many hours to reload everything but man, what a difference! Not a single beachball, no random pauses, no crashes and the system just seems snappier! I also ended up freeing up a couple of hundred gig of disk space for stuff I am no longer using. I always thought OS X was supposed to handle upgrades much better than Windows did, but not in my case. Anyway, it's like a brand new system.