I have a 2011 Air and it definitely runs slower. Specifically when I open a new app or window it takes longer. It also eats up a LOTran more RAM and the machine gets hot. I'll see if I can tweak the settings.
UPDATE: Actually, there is not much to tweak. I updated java and then rebootedslowly at first but after rebooting and it seems to run faster than mountain lion. I think the reboot helped the most. We'll seeMountain Lion.