There's a thread just started on the front page at JavaLobby (http://www.javalobby.org) about open source chart libraries*. If anyone wants to share their experience with a wider audience that is a good place to do it.
I'm always interested to hear what people like and don't like about JFreeChart, so whether you post here or there, please keep sending in your feedback.
Regards,
DG.
* At least I think they're talking about charts. JFreeChart is mentioned along with JGraph ("graph" as in graph theory, not quite the same as charts).