It's the "same" SloppyDOM as Roxen has been using.
It's not complete, in the sense that you can do everything with it, but if your primary interest is in parsing an HTML page or a XML document and looking at a few nodes, it's much easier and faster to use than Parser.XML.Tree.*.
I think it would be nice if we were able to reduce the number of XML parsers in the future (7.10 or so). But merging all of the ones we have, keeping the important properties of each version, isn't easy.