This is what we do too, but this isn't going to kill IE6. It's not a problem that sites support it, it's a problem that large companies and non-techies don't want to or know how to upgrade. What I do for all my sites is add http://pushuptheweb.com/ to all my pages and customize the message to say they're not getting the full experience and that their browser may be unsecure.
I disagree, I think that techniques like this do contribute to killing IE6. The reason that corporations don't upgrade their browsers is pretty simple: they don't have to. As it stands now, IE6 is "good enough" for their employees to do whatever it is they need to do. The more websites that drop IE6 support, the more IE6 becomes "not good enough", and the more pressure accumulates for corporations to upgrade. Right n…
However, large corporations that aren't upgrading probably aren't encouraging, nor do they want, their workers to be visiting cutting edge sites. Usually the computers/browsers are used for company intranet stuff, which doesn't require advanced features. If anything keeping workers from visiting new, cool, cutting edge sites (regardless of what they may be) would actually be incentive to stay with IE6. I do concede, though, that there probably is a fair amount of necessary browsing to other client websites, distributors, etc that needs done.