From The .NET Guy:
I used to use XHTML for my site and blog, but I don't any more. If you want to know why, Ian Hickson is the guy who convinced me. I do believe that the issues he brings up and real and important.
I'm going to partially disagree. Having read Ian's argument, I think he ignores a very real and important phenomenon: the standards aren't set in stone. Things on the Internet frequently evolve when a bunch of people decide to do something, it breaks a bunch of other things, and the authors of those things then fix them to work with the new stuff. Observe the recent rapid evolution of blog reading software.
In other words, the fact that XHTML doesn't work with existing software doesn't mean we should avoid it in all cases. For example, using it in RSS feeds might be fine, since the software for RSS readers is still evolving rapidly and can quickly adapt to the changes. And it's easy to see that XHTML is easier to parse than HTML 4.01, which can have all sorts of nice benefits.
Notice that I'm not arguing for a complete switchover to XHTML right now today. I agree with Ian's points that it is currently problematic, and I probably wouldn't go that route if I were authoring the main page of my company's website. But not everything I do is that mission-critical, so I won't eschew its use, either.