I'm surprised I missed this before. But yes Windows 7, an operating system not even released has already surpassed the latest version of Mac OS.
During September Windows 7 usage accounted for 1.52% of traffic measured by Net Applications, and as of this last weekend it broke 2%.
During the same timeframe 10.6 (Snow Leopard) which was released the previous month, accounted for just 0.77% of traffic.
I'm willing to bet with a few weeks of launch Windows 7 will eclipse the entire Macintosh user base. I'll be very interested in October's figures too to see how close it gets.