I think the argument of what browser(s) you do/don't support really depend upon your site's focus.

I'm pretty sure if Gruber/daringfireball.net dropped all IE support, his traffic decline would be close to 0.

On the other hand, if codeguru.com did the same, their traffic would probably drop off close to 75+%.

If your budget is tight or skills limited, focus on your target market first and make that experience the best you can. Though, that pretty much applies for browser support as well as many other things.