Its been over a week now since I installed Lion and I have to say my opinion of it has changed quite a bit since I first upgraded. Initially I really disliked Lion for the simple reason that Spaces was gone and Command Center functions quite a bit differently. My biggest complaint was that Spaces allowed for multi-dimensional virtual desktop configurations and I had a 3x3 grid that worked absolutely perfectly for my workflow. I have since gotten over some of my initial issues by adapting my workflow and accepting some of the limitations of Command Center. Overall performance is definitely better, my Core2Duo iMac (running Lion) is nearly as fast as my significantly newer i7 iMac which is running Snow Leopard. I really love the changes to Mail.app Preview.app and TextEdit.app, they are a lot more functional now than their predecessors. All-in-all I am definitely coming around to Lion but I still don't think it's a situation where people absolutely have to upgrade.