Can second SpeedRunners. They’ve even announced SpeedRunners 2 recently. The only downside with the game is that when you master the mechanics in the game you can’t really play with your friends anymore, unless they are also keeping up. But even then I think I played the game many tens of hours with my friends before I got addicted and got ahead of them.

Dunno if you know this, but the whole video side of escapist resigned and started their own worker co-op called Second Wind.