How Insignificant Is Internet Explorer These Days?

Maybe Super Tuesday got me in a mood to play with numbers tonight. I was poking around analytics stats for DueProps and noticed that my users are not fans of Internet Explorer in any significant numbers and among them, most use modern versions of IE (8,9) by a huge margin. These visit percentages are across many tens of thousands of visits since we opened our beta last year. 

Admittedly these numbers reflect an early adopter crowd, but still, they're much smaller than I would have guessed. Does this information mean we don't need to invest much effort in maintaining compatibility with IE? Does IE9 have enough penetration to be the only one to worry about?