With web stuff, feelings I have about the value of standards take a backseat to "getting the damn thing working and out the door." That being said, I send XHTML with the text/html mime type.

I prefer XHTML because it is cleaner to work with, and I send as text/html because it most often works.

As far as W3C and Microsoft beating their chests at one another, I've lived through plenty of that. Sometimes I agree philosophically with Microsoft, more often I agree with the W3C. But it doesn't much matter when what I'm sending out the door is the practical solution, not the one that makes me feel warm and fuzzy.