My changes to the plugin have been pushed into a branch:

https://code.launchpad.net/~aflegg/valable/jaffa

I've also made contact with the other developers to make sure we're not duplicating any work.

Current focus: trying to access libvala through Java (by converting the vala-1.0.vapi into something JNA can handle) so that code complete can be as intelligent, and context-sensitive, as we're used to in Eclipse.