There’s a story on pingdom that says, based on web analysis:
“Windows 7 launched in October of 2009, then…
- Within three months, it overtook Mac OS X.
- Within 10 months, it overtook Windows Vista.
- Now, two years after its launch, it’s finally overtaken Windows XP”.
They’ve got more info and some nice graphs that tell us Windows 7 is 40.39% of web traffic (XP is 38.34% and Vista is 11.3%).