I paid $49 for Unreal III, it still sits in my drawer unused and unopened. Why? Because Epic promised to have a Linux port soon after release like they did with UT 2004. That had been the 3rd game I bought from them. I've bought none from them since.

I have not had a single negative experience with Valve. I started with them on Windows years ago and when they came out with Steam for Linux last year I installed it and got all my games (that ran on Linux and more since that have been ported) in the same UI, better experience, faster, I have zero complaints with Valve and Steam.