I personally am on the side of @annybs with the opinion that this kind of thing ahould not be utilised. What's wrong with spending a little extra time ironing out bugs by usin a seperate stylesheet? Or (god forbid) hacks? Chris Coyier of CSS Tricks posted a handy guide on browser specific stylesheets, without the use of hacks. Hell if you care to take a look under the hood of Fireboy Design you will see how we've done exactly this.
IE6 is kinda like your grandad, old fashioned, a bit slow, falls over every now and then. But it will never be forgotten that he is a reminder of how it all started, and how if it wasn't for him the browser world wouldn't be such a nice place to be.
So, without wanting to blow our own trumpets, we'd like to tell you that we design and build standards compliant, IE6 compatible websites.* Thanks for your time.
* note - at no extra cost and without whingeing about it ;)