PyNodes, the bare basics I know it's a very new thing (post 2.4 era anyways) but there seems to be very little documentation and examples for PyNodes in general, and the little there is doesn't seem to work in latest SVN (currently r57165).

My idea is to make a Cycles material node that has a vector output socket for each of the object(s) UV Maps, so that I don't need to look up what the name of the UV Map is in the Object Data Properties and copy-paste that into the Attribute node each time. This seems like a reasonably easy node to code, failing that even just a node like the Attribute one that can fetch an objects Custom Property to be used in the material.

Either way, I'd like some help in setting up a simple PyNode like that. Is it possible? Can someone provide example code of simple working PyNodes?
PyNodes do not make it possible to extend Blender Internal, Cycles or the compositor with new nodes.

They are designed to make user interfaces for new node systems. For example developers of external render engines can use them to make their own shader node systems, or an addon could make a new geometry node system.

It would of course be very useful if they did, but that would be a much bigger project, as it requires each node system to expose an API with access to its inner workings. For Cycles the closest you can get is Open Shading Language nodes.