* A journal is now a bunch of threads rather than just one big one, so all the things like quoting and linking to individual comments will "just work." It also won't be such a performance issue for the server.
* Your PM counter and "Post a new message" links are now on your journal page (thanks jwalsh for the suggestion)
* The archive now works in a somewhat more accessible way.
* RSS 0.91, 2.0, and Atom feeds are exposed.
The big task that I still haven't quite sorted yet is the data transform needed to port all the existing journals over to the new format.