http://entertainment.newsforge.com/entertainment/04/06/21/1510212.shtml
About a year and a half ago the tiny independent game developer eGenesis decided to create a Linux port of its massively multiplayer online game, A Tale In The Desert. The game was designed to appeal to creative people looking for an alternative to games that focused on destruction. The company’s initial thinking was that it might get a few incremental sales and garner goodwill with the community by supporting Linux. What eGenesis discovered was that, per user, Linux gamers were and continue to be their best customers. Each account, on average, has generated twice as much revenue as those of Windows gamers.
That’s about 1% of my total sales
so I guess that stacks up well.