Apple has released Java 1.4.1 through Software Update, which greatly improves the speed and responsiveness of all the TouchGraph applets - including PubMed Browser - in Safari. They still don't work too well in Camino though, for some reason.
Tips for PubMed Browser:
Switch the node label to show ALL lines to be able to see the full titles.
Click in a blank space, then drag to move the whole cluster around.