According to data from Valve's Steam Hardware and Software Survey for the month ending May 2014, Microsoft's latest operating system usage has increased to a combined total of 24.98% (up from the previous month's 23.66%) for both Windows 8 and Windows 8.1. This factors in both 32bit and 64bit of Windows 8 and Windows 8.1.
This data is collected by Valve's Steam game client, for those that did not know, and measures hardware and software stats on a monthly basis. This data indicates how much share an operating system has (among other stats) when it comes to gaming via Steam.
The data indicates that Windows 8.1 64bit saw the biggest increase, with a share of 15.56% (up from 1.66% from the previous month). Windows 8.1 32bit is down to 0.40% (down by 0.01% from the previous month). Windows 8 64bit also dropped to 8.58% (a drop of 0.28% from the previous month) while Windows 8 32bit dropped to 0.44% (a drop of 0.05% from the previous month).
Windows 7 64bit, on the other hand, went up to 50.46%, an increase of 0.44%. Windows 7 32bit decreased slightly to 11.60%. Windows, as a whole, accounts for 95.35% of the operating system usage.