MacBook Pro Retina lag when switching workspaces
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.