These documents describe why I'm not using xhtml:

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.