I have the May/2011 iMac and it's starting to seem sluggish. I've got about 350 of the 500GB used up. Not really sure where it's all coming from, but I do have home-videos in iMovie, so that probably sucks up most of it (I guess I do know where it's coming from). I have Mountain Lion installed. I was thinking about saving everything (just the iPhoto pics, iTunes library, and videos) and doing a complete clean install with snow leopard. What say you?