I have the same issues with my 13 inch retina pro... the UI is anything but snappy or fast, and I'm not talking video editing. Simple tasks like Mission Control, switching between full screen apps, scrolling through mail, etc. - just come with a huge lag. My last machine was a mid 2009 15 inch MBP, I loved it. After the rMBP came out, I thought now it's time to switch. I ordered the 13 inch rMBP with the i5, as I didn't plan to use it for processor heavy tasks. I write and read a lot, so I thought the i5 would do. Wrong! In my opinion the performance of the i5 configuration is a serious joke for a laptop with this price tag. Honestly, if you plan on doing a little scrolling or zooming, get another laptop! On the other hand, I completely fell in love with the build quality of the machine (which is absolutely fantastic) so I decided to take the i5 back to the store and upgrade to the i7. Now, good things first: there is a considerable difference. However, the UI lag is far from gone! I have to say, it makes me kind of sad that Apple throws an extremely high priced laptop on the market (in a presentation full of "Awesome", "Outstanding", "Fantastic", "Georgeous", ...) and the performance - and I want to stress that I'm using my rMBP for reading and writing more than anything - just *****. Sorry to be that blunt. I just can't understand by any means that this machine has made it through product testing and I'm going to say the infamous sentence here: "This would have never happened under ...". Anyway, I hope this thread really get's attention and Apple is working on a fix. After the release of the last WebKit update, which truly bumps Safari performance significantly, there's at least hope that there is one.
