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You should have posted this in the number of threads where people already have their MBP but,

Some (who have had previous MBPs) report that it does run cooler. I cannot attest to the validity of this.
 
It depends on the environment as well.

Just for reference: (Penryn MBP Feb 08)

Currently the temperature in Singapore is 28 C, my CPU averages at 39 C and my GPU at 67 C with just some light surfing. This is 30 minutes after running 3DMark06.

In an air-conditioned room of 22 C, my CPU temperatures drop down to about 32 C and my GPU temperatures drop to 57 C.
 
When using just the 9400M card it is very cool. When I turned on the 9600M GT, it got kinda hot. If you're not doing anything requiring the other performance GPU, it will run pretty cool IMO.
 
This machine is very very cool running even on the 9600 GT when just in osx doing stuff.

When playing a little TF2 last night running in Vista 32bit the machine did get very hot on the Left side only (the "WASD" keys were hot to the touch, same with the underside)

The right side of the keyboard and underneath stayed cool

One thing also to note is that the fans slowed down / machine cooled off after only about 1 minute out of the game.
 
With the 9400M it's very cool. I've been using mine on my lap for the last hour. CPU is about 43C right now. GPU is reading 40C. With the fans at 2000RPM (default), it's almost dead quiet.
 
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