The way I see it, the point of alt stylesheets is so that the user can easily swap between them. Catering to IE with all this extra code only means that there's no pressure on MS to adopt the standards. Why should they bother getting their act together when the webmasters will do it for them?
Just provide your stylesheets as is. If they can't view them, they can't view them. Too bad. Maybe include a note to tell them that they're missing out on stuff available in every other browser.
Besides, your page should still work without any stylesheets, so they are not vital.
On a personal site I'd agree with R1tchard. I provide an alternative style on my site but don't bother to make it accessible to IE users. If they want to use IE then they can live with the single style.