Now Steam Client is available in Ubuntu Software Center (for 12.04/12.10/11.04/10.04). They had already announced the beta release few months ago, followed by new drivers from Nvidia. So, finally, Gaming is fun on Ubuntu/Linux!
Not all cool games are available for GNU/Linux platform, but it’s expected to grow fast – here is the list of cool games available for Linux. You can also try few games for free e.g Team Fortress 2.
Note : There is 50-70% discount on all Steam for Linux games, until Feb 21.