try playing in fullscreen/ turning down your resolution? and check if anything running in the background could be causing it.
Steam only do auto update for amd cards only, if you use nvidia or intel graphics you will be redirected to the respective drivers download website when you try check for video drivers update. Extra: Also, I could run the game on my nettop flawlessly, with no input lag at all. I also tried castle crushers, with some input lag. Who said netbooks can't play games?
Hmm... That is interesting. I just switched over from a computer using AMD to a computer using NVIDIA. That is really useful information.