When I got my rMBP I didn't put anything on it to get an idea of what the standard temps were. After a week I installed the Wrapsol top and bottom case (not the wrist rest) and there was no discernible difference from naked to wrapped. Hope that calms your fears a bit.
I'd like to note that the Wrapsol is incredible. I've always used it on my iDevices but never my MBPs. You literally cannot tell it's there. It matches perfectly and is the perfect thickness that nothing feels different once it's on.