Sorry for not helping myself.
I think Valve made the right decision to start with Ubuntu, simply because it's the most hyped Linux distribution.

But it is indeed possible to run Steam on Debian (the mother of Ubuntu).
Arch is probably a great distribution - and I did use it for almost a year.
It wasn't without frustration, though. So I dumped it for Debian Sid.
Simply because I don't have the time, nor the patience, to tinker - it should just work.
Ubuntu never gave me that either, because there are so many things you need to tweak (as a power user) - and then it breaks frequently. Of course, the dist upgrades breaks, but not only that: the maintenance updates also breaks from time to time..
With Debian Sid I dist-upgrade once or twice a week. Rolling release is great.
Sorry for the hi-jacking.
I will shut up and figure out what OpenGL I have installed now and help testing OpenGL 3+ instead of ranting about Linux distros. :p