Steam just went into Open Beta for Linux. I think they officially support Ubuntu, but I haven’t had any real problems on Mint. Right now the selection of games is pretty paltry, and almost exclusively limited to indie titles, Team Fortress 2, and Psychonauts. At least in my library. The store seems to have a few more games, but mostly just indie titles of various stripes.
If you install Steam, make sure you update your drivers. Every time I tried to launch steam my cursor just disappeared and I had to relog to fix it. When launching it from terminal, it turned out that it was an OpenGL error. Installing new AMD drivers from the package manager finally let me launch steam.
Do you run 32 bit or 64 bit? I’ve read that it’s a 32 bit install, but is supposed to work on 64 bit. I’m on Mint 13 (Maya) 64 bit, and am unable to install. I get the error “The package might be corrupted or you are not allowed to open the file.”
I’m on Mint Nadia x64, and it installed fine. That said, I found out that the current ATI Linux drivers will segfault and crash with Steam, so people with ATI cards are going to have to wait until they fix that.