Digg had an interesting post about supporing IE6, a browser that's so f'ing old that it's staggering anyone still uses it. The good news is that the numbers are very quickly dropping. Before the CoasterBuzz re-launch last fall, it came up in a conversation very early on that many IE6 users are stuck there because of IT departments that force them to use it. Despite that, I summarily dismissed any deliberate effort to support it. It seems to work OK, but if it doesn't, I'm not going to lose sleep over it.
Sadly, my numbers aren't even as optimistic as Digg's, and I've got 13% of visitors still using it. However, I don't think they're the users that really "count," as they view fewer pages and/or bail far faster than the average for the site at large. It still amazes me that there are comprooders out in the world still running a browser that's eight years old.