As an aside, July was the first month where Firefox/Mozilla users outnumbered Internet Explorer users on this web site.
The figures I have seen elsewhere puts Firefox at 10% of users, but apparently the game/academic blog intersection overlaps with early adopters of Firefox. Or something.
I saw the same increase in numbers. It makes sense that people who spend a lot of time on the web would move to another browser. All it takes is one mysteriously pernicious pop up, or malware invasion to make you look for other solutions.