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#1
There is the Steam Hardware Survey as well.
Right now 7 is the latest item in the "hot news room" where everyone is keeping tabs on it. Of course that has also left quite a bit of room for online news articles and blogs to come up at any time and every day with some new page.
Many who stayed with XP or went back to XP after only a brief run with Vista are now trying to dual boot if they got the betas or are now trying to find when/where they can download one. Yet the 64bit Vista Ultimate turned into a large crave there real fast especially for gamers wanting more and more memory.
You know they are now taking serious notice of the 64bit 7! As far as surveys? Those can only tally those who supply information in an online survey or some place like Steam in support requests.
how can they track it? my google analytics doesn't track windows 7
In the case of websites they track it by the version the browser reports, if google analytics does not show it then they need to update their script.
You can see what your browser reports here Browser Mirror - See what your browser reveals
And for some more stats here Operating system market share