I got a lag when I switch between workspaces (four fingers left/right).
Can somebody confirm this?
I assume this is the weak ivy bridge graphics. If this is true only the next generation will fix this....
Try disabling automatic graphics switching (http://serato.com/video-sl/support/5613/how-to-adjust-graphics-performance-for-the-macbook-pro) and see if that helps. It may be trying to use the slower integrated graphics over the dedicated GPU.
Also, you may experience lag when using a scaled resolution. This is most likely a hardware issue but future software revisions may help.