I think, there is a need for a new graph package because:
- yGraph is tooooooooooooo expensive
- JGraph is a fake (cause it uses a TreeModel inside and has actually no extensibility features)
- prefuse is not very mature at the moment
- tensegrity is unstable with bad performance
The problem with all of them: They just focus on the Layouter Mechanism, so they have pretty dynamic and animated force-enabled layouters to display a graph, but if you look inside the details, you get
shocked...
Also the usability is poor: for displaying graphs they are nice, but they fail when you are liked to build an editor with this...
So... if you have time, may be you can base on prefuse and build a pretty user interface for making editors a.s.o....
Good luck!
Robert