Yep, I run Arch but answered Ubuntu because I knew I'd have no chance of getting into the beta otherwise. No doubt someone will manage to create an AUR package for Arch that uses the Ubuntu version of Steam. Unfortunately, I wasn't selected, so I have no way of knowing when I'll actually get to try it out.
The first time I connected it didn't work, but I put in the command to download tf2 (which didn't download) and after that it seemed to work fine, I could talk to my friends and download/play my HIB games.