Got the lag fixed - here's my story. I've had lag from the beginning. I work in Security and know the inner workings of OSX, so I assumed the lag was from software. My mac came with Lion, which had the lag. Waited for Mountain Lion, did the install and it still had lag. To me, there's 2 types: 1) scrolling (based on webkit) 2) overall lag of the GUI I had both. To solve the scrolling lag I updated to latest beta's of firefox, safari which fixed a few things in browsing (quicker/smoother etc), but the overall lag was there. The most noticeable lag for me was expose. Any big window changes just lagged. This was evident in iCal, Expose, Mission Control and gaming. I just had lag all the time. I read as much as I could find about fixes and tried them all. Using the discrete GPU instead of the intel one by using gfxstatus, using the OpenGL profiler, repair permissions, next software update 10.8.1-10.8.4 etc etc..The last one was Spotlight's mdworker constantly logging to console "mdworker unable to talk to lsboxd" so I excluded what mdworker and lsboxd should do. Still lag! This is a beautifully engineered machine. It just shouldn't have this lag! Then I read a great article here about the problem with retina macbook pros was heat. Basically the way the GPU/CPU was dispersing heat. I saw a post on ifixit http://www.ifixit.com/Guide/Reapplying-Thermal-Paste-to-the-CPU-and-GPU/9587/1 on reapplying the thermal paste. At this time, I started monitoring the temperature of the device and noticed, anything above 50-60C caused the display to lag. The hotter it got the more lag. This made sense. It usually ran fine at anything below that no probs. So I was convinced it's not a software thing. So I booked a service into the apple store. I had 3 issues... 1) the Lag, 2) had a screen defect with the white spots (lived with this up until now) 3) the clicking of the base on the back right hand side. Talked to the genius guy, told him the situation and he said he's never heard of the lag being caused by heat but understood and said they'll give it a go and check their internal engineering reports and documents. The diagnostics passed ok. So they changed the display overnight, reapplied the thermal paste and fixed the clicking base. Now.. I got the mac back the next stay (great results!). Been using the machine for the last couple of hours and WOW! - luckily have a new Samsung LCD not an LG - the clicking is fixed - The Lag - well I haven't had it yet! I've pushed the mac to its limits, stress testing the CPU and the GPU. - CPU by running "yes > /dev/null & yes > /dev/null & yes > /dev/null & yes > /dev/null &" in terminal causing the cpu to hit 100% - GPU by running GPUTest http://www.Geeks3D.com/GpuTest/ The temperature monitor didn't go about 67C even with both CPU/GPU maxed out and then the fans kicked in and STILL NO LAG!!!! This is evidence enough for me. Retina Lag = HEAT = bad application of thermal paste. Hope this helps someone else because the next step was to change the logic board and go through the hassle of setting it all up again.