One of the things that I haven't seen mentioned yet in the XML::LibXML vs XML::Twig discussion is that XML::Twig is available via the standard ActiveState Perl distribution, but XML::LibXML isn't (though you can get it by adding the uwinnipeg repository). This means that if you're planning to use LibXML once you leave the prototype stage, but your end product is supposed to be usable on MSWindows boxes later, you'll have to add an extra hoop for end-users to jump through to get it working.