In AnandTechs review of the 13 rMBP, it mentions that the UI frame rate is not always 60 frames per second but can drop significantly below this. Now the 13 rMBPs resolution (2560 x 1600) is pretty close to the 27 iMacs (2560 x 1440), and while the 13 rMBP has a weaker GPU than the iMac, the review mentions the frame rate appears to be limited by single thread CPU performance rather than GPU performance. (Quoting from the review: In every situation where UI frame rate drops significantly on the rMBP, the offending application usually ends up consuming 100% of a single CPU core.) The base 27 iMac CPU speed is 2.9 Ghz (turbo is 3.6) while the rMBP is 2.5 GHz (turbo 3.1) so the iMacs single thread performance should only be ~20% greater. Here my question: does the base 27 iMac have a good (60 frames per seconds) UI frame rate? Ive personally had a play around with one of these iMacs and dont recall having any problems but my time was limited and I was probably not looking at complicated to display web pages etc. Those of you that have one of these, Id love to hear your experiences to date.