I've been using OSX Lion 10.7 DP2 for a couple days, so far love it, only experienced crash with Speed Download, nothing else, quite stable..
I have to say though that the Full Screen feature is a bit of a gimmick, I've never found a moment where I found it useful, at least not yet..
My favourite feature by far is the Launchpad, although its too bad you cannot assign a keyboard or mouse shortcut, also would be nice if you could remove applications from the launchpad, sometimes uninstallers show up, and all it does is clutter things..
The animations are beautiful, as far as performance goes though I haven't really noticed any improvement, also I've found that OSX Lion uses more memory then Snow Leopard, which sucks 😛