Windows gamers are not only quickly shifting to Windows 7, but also 64-bit operating systems. There are over two times more Windows 7 64-bit users than 32-bit, which is the exact opposite for Windows Vista, and there are virtually no 64-bit XP users.
Meanwhile, Vista commanded a quickly declining 21.61%, and Windows' share as a whole plummeted 8.43% from April following the launch of Steam for Mac. Of the new OS X users, 1.4% were on Leopard and 7.06% ran Snow Leopard.
It'll be interesting to see how the divide looks between Windows and Mac machines over the coming months. For instance, how many Mac users will bail after briefly using the service, and how many will get their friends hooked on Team Fortress 2?
You can read Steam's complete hardware survey here, which breaks down information about users' core components, including processors, graphics, storage drives, network speed, and display resolution.