Clean installed my 2011 13" i7 Air with 10.7.4. then installed all the apps I use daily. There is a very noticeable difference in this machine. I already thought it was ridiculously fast. I find the machine boots about 1.2 seconds faster to the desktop. I think there's better graphics drivers all around for the air. Maybe a good bit of software optimization within the OS as well. Everything seems smoother.