No offense, but that sounds a bit... 1998'ish...
I've said it before and I'll say it again:
"This page works best in Internet Explorer 5 or higher"
translates into:
"I'm too lazy to make proper HTML and CSS, and/or rely on amateur IE-only effects to get my site to work the way I want it to"
In the past 2-3 years, you're one of the VERY VERY few people who actually still did that, drop support for anything non-IE.
What I've done is the opposite: drop support for IE and only make sure that the site works properly in IE, all the really spiffy features go to people using a real webbrowser (which, with the exception of the obscure and the text/speechbrowsers, is anything not IE). The response I've gotten so far from these plans (not fully implemented yet as the site that this is happening on is in private development) is most positive, Windows people switched to Mozilla and Firebird and were amazed at how much better those browsers were, how useful their features were and wondered at why they didn't know about this yet.

I've not had a single person complain about me dropping support for IE, but then, I'm a Site +++++ and make sure that everything
does work in IE. Just not as fancy or speedy, which is due to the incredible limitations of IE.