Valve does share the collected information, or at least some of it, and just released their statistics for last month. Most interesting in this recent report is the growth identified in both hardware and software. In particular the use of single-core CPUs has shrunk dramatically, whereas dual-core and even quad-core CPUs have gained in popularity. Dual-core CPUs now make up nearly half of Steam users, and quad-core has passed 10%.
On the software side, Windows Vista has seen real growth. Perhaps a little too late, with Microsoft already busy working on Windows 7. Also interesting was the split in terms of screen resolution – 25% of Steam players used 1024x768, 37% used 1280x960 and 28% used a widescreen ratio (16:9). Whatever the reason, people seem to have a very sharp divide on what resolutions they prefer (or perhaps their hardware can handle).