I am a big "Macbook Pro runs too hot" proponent. So I went into my Apple store installed iStat on one of their new MacBook Pro Retina Display laptops and went for it. I ran HD flash video, I ran HTML5 video players. I went into iPhoto and held down the left arrow key and let the machine run through all the pictures as fast as it would load them.
I kept checking with iStat and am truly amazed. I am not sure if it is Ivy Bridge, the vent holes on the bottom, the way graphics are handed off between the descreet and onboard GPU, but that computer never warmed up to "2011" MacBook Pro temperatures.
I was doing some naughty things to that machine, and she performed like a champ.
I did notice the heat vent under the screen hinge has been redesigned and now there is a bigger gap between the vent and the edge of the screen. Like I said also the vents around the underside of the perimeter of the case might also help out, especially since the vents are located right under where the segmented battery is located.
As far as thermal issues. I am impressed.
The new MacBook Pro 15" with retina display is a marvel of technology. and I look forward to see what the second generation of this product looks like.
Matt Sievert