Terrible GUI lag/glitchiness after reboot in Mountain Lion 10.8.2 I got a brand new Retina MacBook Pro (2.6 GHz Intel Core i7, 16 GB RAM, Mountain Lion 10.8.2) a couple months ago, and it was buttery smooth (for the most part) at first. 

However, one day I turned it on and I suddenly got some terrible lag issues. For example, when I opened the Notification Center sidebar, it stuttered and chopped on the sliding animation. Similarly, the Genie effect stuttered when I minimized windows. The list just went on and on. At first I thought this was a hardware problem (it also turned out the screen had been mis-aligned), so I brought it to the Apple store. They couldn't find anything wrong with the graphics chip, but it they decided to replace my MacBook because of the bad screen alignment. I got the replacement yesterday. I restored my previous system from a Time Machine backup using the Migration Assistant. Everything was buttery smooth again, and I thought the problem was resolved.

However, this morning, I fired up my MacBook again and all of a sudden, the lag is back. The fact that the lag was nowhere to be found right after the Time Machine restore, but then suddenly back after a reboot is mystifying.

Can anybody please shed some light on this situation? Thanks!

UPDATE: I have tried turning off "Automatic graphics switching" in the "Energy Saver" system preferences, but to no avail.
I successfully resolved the glitch/lag problem on my Retina MacBook Pro by re-installing Mountain Lion without use of the Migration Assistant. I have outlined my steps below:

Backed up all my data to an external hard drive
Completely powered off my MacBook
Turned on my MacBook while holding down the &quot;Option&quot; key
Entered the Recovery partition
Used the Disk Utility to reformat my SSD
Re-downloaded and re-installed Mountain Lion
When asked if I wanted to use Migration Assistant, I opted out
Manually reinstalled software, copied over files, etc.

I really think Migration Assitant had something to do with the lag. Either that, or some file or software I had caused the lag, and Migration Assitant simply brought the problem over to my new MacBook when it migrated all my files and settings. In any case, my MacBook Pro is now buttery smooth again, with none of the lagginess and graphics artifacts I had before. I'm happy!
Just for the record, here's all my MacBook Pro with Retina Display system information:

Mid 2012 model, 2.6 GHz Intel Core i7, 16 GB 1600 MHz DDR3 RAM
OS X version 10.8.2

I hope this helps anyone else with the same problem!