[matt1]

In my experience, if you ask the people who use IE6 why they don't upgrade most of them will respond with something like "What's IE6? Oh you mean Internet Explorer. What's wrong with the one I have?" and then if you finally convince them they they should upgrade you have to explain to them how to do it, which for most people who are still using IE6 can be a big challenge.

My grandmother uses IE6. She says it works and doesn't want to bother with an upgrade. She doesn't care that you app doesn't render properly :)

[snprbob86]

    She doesn't care that you app doesn't render properly

I think this is the most important point, but it is made so rarely!

Most people who have IE6 are either too ignorant to care if your site renders incorrectly or know that they are forced to use this browser for some reason. The former group probably isn't using your next gen web 2.0 fancy pants app anyway, and the later group has seen so many broken websites (at work) that they look right past the problems or try again when they get home.

In general, all you need to do is ensure your site WORKS AT ALL in IE6. It doesn't need to look perfect, just not be broken. But honestly, I might just serve them the mobile version with a warning on top...

[thwarted]

That's not a bad idea... serving the mobile version to IE6, because as time goes on, and as more people are using smart phones with modern browsers, browsers that are more powerful than IE6, IE6 starts to look more and more like an ancient mobile browser anyway.