These documents describe why I'm not using xhtml:

• Sending XHTML as text/html Considered Harmful [Ian Hickson] (local copy)
• A warning to others [dive into mark] (local copy)
• Semantic obsolescence [dive into mark] (local copy)
• Eddies in the space-time continuum [dive into mark] (local copy)
• The Road to XHTML 2.0: MIME Types [xml.com] (local copy)
• All That We Can Leave Behind [xml.com] (local copy)
• The Vanishing Image: XHTML 2 Migration Issues [xml.com] (local copy)

The basic argument of the documents is: xhtml provides few benefits, and many drawbacks. Support among 2003-era browsers is painful, even in browsers that claim to support xhtml. Migration is painful; it is very hard to build a site that serves xhtml to xml-enabled browsers while still serving html to other browsers.

The author's conclusion, and mine too, is that HTML 4.01 works well enough for general use. There's no reason to use the latest and greatest xhtml, because the benefits are weak and the costs are high.