I've found a few issues with this last upgrade for Apple OS 10.3. The first and biggest one revolved around a problem wherein people would run the update and then their system would freeze upon rebooting. It got to the login screen and would not go any further no matter how long you would wait.
The problem doesn't ever affect people who have an admin account on the system because their accounts are able to properly overwrite the files that need to be changed, but for people with restricted accounts, it will sometimes be an issue and sometimes not. I thought that the problem may have revolved around Font Reserve or some other software installed on the machine, but all of the tests myself and co-workers did proved so inconclusive that I don't know for certain where the problem could be.
There are a series of steps you can take to fix the problem if it dogs you though. They're somewhat tricky if you're not used to the command line of OS X, so be warned. Also, if this doesn't do the trick, the only thing I've found to fix the problem is a full reinstall, which is painful to say the least.