JGo (Score 1)

Another package you might want to consider is JGo.

It too is oriented around nodes and links, but is focused more on interactive editing than just on visualization. You can construct more complicated nodes than just simple shapes and/or images with text. You can embed native controls and manipulate subgraphs. There are native versions for Swing and for SWT.

This is a commercial product, but you do get the sources for the base library. More information is available at http://www.nwoods.com/go/jgo.htm