Stack Overflow 2010 Analytics
blog.stackoverflow.com
blog.stackoverflow.com
PS: On a similar note I'm surprised China is missing from the list.
More likely, corporate developers of every flavor are more often locked into IE by company policy. It would be interesting to see those browser usage stats broken down by language. I bet Java and .NET would have similar IE usage.
I use IE quite a lot for general browsing. The latest versions aren't that bad, and aren't as memory hungry as Firefox.
Nothing too interesting, really.
While I appreciate there are a few hardcores who will want to answer questions on the go, I can't see that being a big priority.
I answer less questions than I normally would if the interface were better.
(maybe this is fitting into the definition of "a few hardcores" for you though)
You're also focused on the users of SO specifically. There are Area 51 sites that would be more prone to having users on mobile devices.