I have the "older" March 2009 2.66ghz model and was surprised at how cool it runs. For the record it uses a 35w T9550 processor. I have yet to use the 9600M GT card in Leopard because the 9400 works just fine so far.
I have been a PC guy since, well....forever, and one of the biggest complaints on a PC laptop is heat. Owner forums for Dell, HP, Acer, Toshiba etc. all complain that the laptops run painfully hot and render the keyboard/trackpad virtually unusable. I can attest that my model MBP running OSX for hours straight (both plugged and unplugged) has never produced any heat issues. Yeah, if you are a multitasking fool like me running everything possible at once, you definitely feel heat around the left function keys and left speaker if you run your fingers over the aluminum, but is it a problem of any sort, absolutely not.
I have set it comfortably on my bed or my lap for a long time just streaming Netflix and doing basic web type stuff and it never gets even luke warm and runs absolutely silent.
I also installed a legal copy of Vista 64 I had, which only sees the 512mb 9600M GT and has no fan control, and I am pretty sure I could have lit a cigarette off the unibody frame after just a few minutes of use. In that instance, it actually hurt to touch the frame. Seriously, it hurt. I could be wrong but I thought I saw it glowing red after about 30 minutes of updates. Yep, it got that hot.
No mas Vista for me.