Opensource radeon driver is pretty good if you don't need 3D. I would actually say that it is much better then the AMD one - there are no problems with suspend and the card initializes more quickly.
I take it you will need 3D if you are in the market for Steam.
I also went through all sorts of hell with proprietary AMD/ATI drivers, and I needed them for OpenCL. To this day my Desktop is a pain to use but OpenCL works fine. Sadly they make the best cards for this purpose by far, otherwise I would get something else.
