I've been on a distrohopping spree lately, and in the process I have been back and forth between Ubuntu 11.10 (with Unity removed and gnome-shell installed) and stock Linux Mint 12 (based on 11.10). I've had fresh installs of both two times each.
Both work great on my laptop (Inspiron i15-RN5110, Core i3 and onboard Intel graphics) EXCEPT that with Ubuntu the fan will regularly go nuts. I run top in the terminal and nothing will be eating cpu, but they fan will be going crazy and then go back down again. The laptop is not hot but it definitely feels a little warm.
With Mint, the laptop is cool and the fan runs low.
The riddle I want to solve is if Mint is based on this same version of Ubuntu, what are they doing to make it run so cool and calm? For various reasons not relevant here, I'd prefer to keep running Ubuntu if I can solve this (if not I'll have to go back to Mint).