You know, at first I was also scared about how the Speck See-Thru case (I have the completely clear, transparent one) would effect the temperatures of my MBP.
I remember on my 12" PBG4, I would see the gpu get around 84 degrees celsius and the cpu 75 celsius after an hour or so of WoW, and I saw very high temperatures in other Apple laptops as well (iBook G4's for example). I had also heard that the standard MBP's had high temperatures too, so I stayed away from these cases for a long time.
Well I'm happy to report that after an hour of CoD4 Multiplayer, the hottest part of my computer, the cpu, hit a maximum of 68 celsius (Around 150 I'm guessing) which is well within good operating temperature.
So to those of you worried about temperatures, don't, the Unibody really seems to handle heat well. I'm very happy about that.