The only hesitation I'd have with POD is that it's not terribly extensible at the text level.
in reply to Creating Books and Manuals with Perl
With POD it's easy enough to add new paragraph level directives using =for and =begin/=end, but there's no way built into POD to add new X<< ... >> directives. Partly because there's only so many single letter directives to go around, and partly because POD parsers just don't support this kind of extensibility.
So if you expect to be using footnotes or endnotes or index hints or any of those sorts of other extended things that need to go at the text level rather than at the paragraph level, I would go with XML. Don't worry about what syntax of XML you use, be it DocBook or XHTML or TEI or invent your own as you go along. It's always easy enough to transform between one syntax or another with XML using XSLT or other transformation tools like a SAX filter.
If you feel you can live without those features, then I'd say go with POD. It's really easy to author, and quite readable from an editing perspective, and when it comes down to rendering it to different formats, the tools are pretty much second to none.