I run gentoo on my laptop, and I undervolt it, it requires specialized kernel sources, but the laptop runs quite a bit cooler with undervolting, since I could undervolt it stably from 1.396V to 1.150V, which I think is a pretty good drop, that's how I lived with my laptop for 6 months with a dying cpu fan, lowest speed mode and undervolting. If my laptop was idle at 2.13ghz mode, it would idle at 60-65C, which might be a bit hot, but that is on the highest speed setting constant, not dynamic speed settings, which is I think what ubuntu does for example. Not sure if it is possible to modify the ubuntu sources of the kernel for the undervolting, but I used what's known as emission sources on my laptop. Just thought I might mention that, though I have finally sent it in for repair to get my hard drive, ac adapter, main battery, and cpu fan replaced, I ran it into the ground, and yet I ran it in that state for 6 months, so, meh.
JDGBOLT