Mountain Lion 10.8.2 has fixed most of the laggy issues.
And the rest of it is actually because the 15" rMBP suffers from a bug with the EFI interface that causes it to downclock the CPU to 1.2GHz indefinitely (restarting or powering does not help) until SMC parameters are reset.
Since OSX still uses the CPU to render a good part of its interface, that resulted in laggy animations for a lot of things.