I'm having problems on a late 2010 MacBook Air. I'm a new mac user, and have been very satisfied with hardware and OS (some things I don't like about OS X, but that's another story). I've updated to Lion mainly for the full disk encryption feature.
I've been having multiple crashes, in different forms. There are a lot more slow downs than with Snow Leopard (I basically didn't have any) and some of those slow down's turn into crashes or permanent unresponsiveness. Last one, safari suffered one of these slow downs upon opening a new tab, this disabled the menu bar, changing to another application enabled it and I could go to the "Force Quit" option (didn't know the shortcut yet), Force quit menu didn't appear, another application stopped responding, etc. Always the same cascading effect until the system is unusable.
I'm kind of pissed at this, specially considering how well the system worked before.