Steam conducts a monthly survey to collect data about what kinds of computer hardware and software our customers are using. Participation in the survey is optional, and anonymous. The information gathered is incredibly helpful to us as we make decisions about what kinds of technology investments to make and products to offer.
PC Video card usage by mfg

DX10/11 Systems (Vista/Win7 + DX10/11 GPU)

PC Processor usage by manufacturer

PC Number of CPUs per computer

Mac Hardware ownership

Mac System RAM