Installing the ATI catalyst drivers for my video card cleared up so my any issues. I can now run steam games with the steam overlay, which means I was able to turn on the framerate feature so I could get real numbers on performance. I was unable to do that before.
So far on the two games that I have tested in steam and on linux (L4Dead 2 and Borderlands 2) I am getting solid 60 FPS in normal game play. Sometimes it drops down to 36FPS when the action gets real crazy, for example when you have 50+ zombies trying to chew on your butt all at once, my frame rate drops to 36.
I did also notice that with the old drivers the textures in Left4Dead 2 were messed up, the bald guy had a strange looking graphical glitch that made him look like he had a mowhawk; One of the other characters had a glitch that gave her a big black blotch on her chest. Those issues cleared up too. Nice to know these were driver issues and not defective hardware, which is always my worry when I see glitches.
I also started monitoring load and cpu temps, my load will spike up to 3 in L4D2, but the temps stay low at around 56c. I've been reading that 80c+ is when you need to worry about it. So that's good news. The system load hovers aroun 1 and 1.4 during normal game play. That I think is acceptable. Using htop I can see that it is spreading the load across both cores and both hyper threads pretty evenly.
Over all, I am happy with results I am getting with a system that was never really meant for gaming.
Will this be my main gaming rig? No, but I will play on it when I just feel like playing a quick game or two. Will I convert my Windows gaming rig to Linux? Not just yet. We are almos there, but there are still some games that are windows only that I like, and I don't want to deal with WINE. I think when we start seeing linux ports as a common/normal part of pubishing new games, then it will become my primary OS for gaming, until then I will use both, Linux for the games that are support and Windows for when I want to play games that are Win only.
I'll post updates on other games as I install and play them, maybe I can encourage others to start gaming in linux.