Generally I find the mailing list format to be sufficient to keep up with current messages; however, it can feel inadequate when I want to search or browse older messages from before I was subscribed to the mailing list.
If there were an interest in adopting a forum, I would highly recommend keeping the mailing list and setting up a forum that mirrors it. Users can post to either the mailing list or the forum, and the message is mirrored on the other. A great example of this in action is the OpenSceneGraph forum (
http://forum.openscenegraph.org/).
Cheers,
Kevin