With Mystic Mine, a majority of the gamers are running Mac OS X (42%) followed by Linux with 34% while Windows gamers only account for 23% of the sales. Wow. Of course, this isn't the situation for most games where there are by far more Windows gamers, but this figure is important nevertheless. Koonsolo also published their web server statistics showing Linux users had the highest conversion rates for making them a sale.
Their numbers and more details can be found on the Koonsolo blog.