Super Tux Kart is the most enjoyable "linux" game I have played in years. It is not without its rough edges but has lots of appeal once you give it a chance. I load it up when I have a few minutes to waste by the computer, such as when I'm listening to an audio file or on hold on the phone. It's enjoyable even in quick bursts and with the sound off and reminds me of how I fell into video games in the 90s. It offers plenty of action with little time investment and keeps me coming back with its variety (there are loads of maps and game-modes). It's still in beta and with every update the graphics have improved and the gameplay has been tweaked (strangely often getting worse but at least there's always a new challenge).
In my opinion the Zero would really benefit from a port like this. With respect to the likes of Apricot and Worship Vector which are brilliant for what they are, the "indie" games made on a larger scale, not only on the Zero but in general, have so far been disappointing and not capable of attracting or exciting the masses. While on the surface SuperTuxKart uses a played-out formula similar to "Mario Kart" and "Crash Team Racing", it is actually quite unique in that it doesn't feel like a counterfeit or streamlined rip-off of a proprietary title. I suppose the Windows-alternative themed characters help give it it's own identity and with the network-race option (and the fact that the game is a free downloadable) it has the potential to be more fun than the games that inspired it. For those reasons it can be used as a showcase for the potential of open-source gaming (whether games or platforms). It is not the most complete or polished "linux" title I have tried but critically it is one of the best and has the ability to impress both casual and hardcore gamers. It has as much substance as style and like the Zero it should get much better over time.