Benefits of polyglot XHTML5

In order to come to terms with HTML5 and finding out, what happened to
XHTML, I have made a tutorial:

"Benefits of polyglot XHTML5",
http://www.xmlplease.com/xhtml/xhtml5polyglot/

Nice to know if I have forgotten something or if things need to be corrected.

Cheers
Jesper Tverskov
http://www.xmlplease.com