DomXPath extension

Hey guys, I've been working with the DomXPath class and would like to use the 
full XPath vocabulary for searches.  But before I go trying to write an 
extension that does this I'm just wondering what the current status is and when 
you all think everything is going to be supported.

I'm mostly interested in making XPath functions work (e.g. count()).  But no 
sense in re-inventing the wheel if someone else is already hard at work doing this!