10.3.9 has a significant java bug

Best places to read about it: OS X hints: macosxhints - A fix for broken Java after 10.3.9 upgrade and Apple.

Overall 10.3.9 sounds promising but imperfect. I'll wait another week.

Update: Sounds like it's caused by having java running somewhere (other user space) preventing the update. In theory this is allowed, but in practice here's the superstition I follow for major OS X updates (XP updates, in my experience, have not required this sort of superstition):

1. log in on my very plain admin account (no odd configuration, no startup items, etc). Run PCC (or similar) to flush caches.
2. shut down, restart and login again to admin
3. run the update
4. shut down and restart

I sometimes "repair privileges after #4, but I think that's less important.