My 15" MacBook Pro shows two fans. Fan 2 seems to always spin faster than fan 1. (I can get Fan 1 to drop to 1000 RPM, but fan 2 seems to have a minimum of 2000.) But, my goodness does my computer's temperature drop when I force it to run at 6000 RPM. (Although it is then louder than my eMac.) When encoding H.264 with both processors maxed, it drops over 50°F. (194°F to 140°F.) And it feels noticably cooler. At 3000 RPM (the fastest that it is still 'quiet',) it helps, but not nearly as much. The top feels warm; but not quite as warm as if I don't use it.