The beta for Ubuntu 8.10, code named "Intrepid Ibex," is now available.
I'm downloading it (ever so slowly) now.
Some new features include NetworkManager 0.7, so that you no longer need to log in to get a network connection (long overdue), X.org 7.4, and updates GNOME to 2.24.
No idea what the last two mean, they appear to basically be incremental improvements. So nothing too major this release, just general improvement.