Just wanted to share this! I have early 2011 higher end MBP model. I even did a clean install a while ago but nothing seemed to help for my temperature problems. My fans would easily be 4000-5000rpm while listening to Spotify and surfing on Facebook. MacShop said there's nothing wrong with my computer. I know my partner has the same exact mbp but he has never had any temperature problems. My left side of the keyboard was always hot. Temps usually 65-80 degrees. But yesterday after upgrading to Mountain Lion my mbp is a lot cooler. No more hot on the left side. And right now I have Spotify, Safari, Mail and Calendar open my CPU temp is 40 degrees. I can't believe this. Now this feels like MacBook Pro should feel like. So if you think you have temperature problems (I have been thinking that since the day I bought this machine early 2011) you gotta try Mountain Lion!