About a live demo, maybe in a few days it could be possible (not depending directly on me).
About Ajax, I agree with you about making a new package for a complete Ajax UI, but what I want to add are only simple actions, such as "click 'mark as read' button". If the browser is not javascript compilant, it has not enabled that feature, the current link will work as it actually does.
I'm thinking on a forums enhancing, not on a complete rewrite of forums using (almost only) Ajax, so I think a few Ajax requests should be too bad.