There are some compelling warnings about the usage of XHTML, primarily centering around the fact that the mime-type for such a document should be sent as:
Content-type: application/xhtml+xml
Yet IE 6 and 7 don't support this, and then websites must send it as:
Content-type: text/html
Unfortunately that method is considered harmful.
Some also bemoan the fact that although the intent of XHTML is to make web pages parsable by an XML parser, it has in practice failed due to incorrect usage on existing websites.
I still prefer to write documents in XHTML 1.0 Strict, mostly because of the challenge, and the cleanliness and error-checking that a validator gives. I enjoy the syntax a bit better, because it forces me to be very explicit in when tags end, etc. It's more for me a personal choice than purely technical.
