It's a M004U (AKA CN60). I should also have mentioned that I bumped the RAM to 6G (though 4 would have been fine). CPU is a Celeron 2955U, 1.8GHz dual core.

Fan's moderately loud. It seems to only come on when the GPU is stressed, rather than the CPU (playing 3D games, essentially). Doesn't come on when I'm playing movies or compiling code.

I run Arch with XFCE as my desktop, which I admit isn't very demanding - but it's zippy. Can't say what it'd be like under Gnome/KDE, but if I had to bet I'd say it'd be fine.

Installing Linux isn't for the faint of heart, but there's some good guides and it doesn't take long.