There are a few, the exif docs already use it. And they also live within the unofficial official phpdoc wiki:
http://wiki.phpdoc.info/DocSkel/FunctionskeletonDotXml/
Could someone please collect all the sites already set up with docweb stuff, wikis, pepr copies, livedocs and stuff, so we don't continue with more sites getting up and going down? It would be nice to summarize the situationon docweb@lists.php.net. I must admit I am getting to loose the picture (who owns what domain, who is going to set up what, what is going to point where, or at least what is the intention).
Goba