So I just turned on my 3-month old rMBP (15/2.3/16/512) and found it was behaving incredibly strangely. To start with, I noticed that the video playing was jerky. I know the the rMBP will have the occasional lag issue, but that doesn't bother me. But trying it with Safari, Chrome and just moving windows around showed that the screen was struggling to properly VSync. I tried this with Intel & nVidia Graphics as well as completely disabling gfxCardStatus, but the problem remained. So the issue I noticed right after that was that Mission Control was lagging incredibly when activated either by button or gesture. Like, it would zoom out the wallpaper, wait a second then the windows would jerkily follow. There would also be graphical glitches (like the sort when you change screen resolution) around windows and the dock area (moving the dock to turn off transparency didn't help). What is weird though that Launchpad and swiping between desktops was just as smooth as usual, bar the VSync issue. So I thought to run Apple Hardware Test and just make sure no obvious hardware defect was starting. I followed the apple guide and held down 'D', but nothing happened. So I tried every key combination involving D, Command, Ctrl and Option but I just could not get it to boot into AHT. Next step, reset SMC and NVRAM, just incase. Resetting the SMC was fine, but when I tried to follow the guide on Apple Support to reset the NVRAM it didn't work. The key combination Apple gives instead booted me into the recovery partition - I tried twice to be sure. So, as a final ditch, I repaired Disk Permissions. While it did come with the following interesting messages: among other services that were wrong, upon a restart nothing has changed. I also verified disk just because, but no problems were found. So I am stuck. I am loathe to bother with Apple Support in the first instance because I would really rather not have to install ML and because I got Samsung screen AND SSD I don't reeeally want to replace it. Also, the support at the nearest Apple Store I really do not rate, and at this moment I cannot really be without a good laptop for long. So does anyone here have any experience with any of these problems, and a possible fix? Thanks UPDATE: I downloaded and ran Quartz Debug, and that somehow fixed the VSync/lag issues. It seems as if it forced Quartz Extreme to enable or something. So, does anyone have any advice about getting to the Apple Hardware Test?