Searched elsewhere for this, even tried to get Apple Support to help but they say it's a software issue, and want to charge me, so I thought I'd post here first! Anyway, on random occasions my stock 15" 2.3 rMBP has serious performance issues. Skipping playback (like dust on a vinyl) within iTunes 11, sluggish text entry, sloppy framerates in 3D games etc. Wanted to post here to see if anyone has had the same issues, as when it's performing well, it's quicker than my Mac Pro, but when it isn't it's worse than my previous MBP Core 2 Duo, and it only seems to happen randomly, i.e. not when running on battery or if any particular App is open. Totally lost on this one, and don't really fancy taking it to an Apple Store, and have it taken off me for a couple of weeks whilst the try and fix it. Any help, or people with the same issues, would be much appreciated!