I was a bit hesitant to upgrade to 4.0 due to a change in major version number and also because it was still not a GA release. However, I experimented on one server and the upgrade was as smooth as all earlier ones.
Only difference was that until now, I was using RHEL binaries and was never warned that this is not for my platform. This version warned me once that I am on CentOS4 and the binary is for RHEL4, so I cancelled the upgrade once - went back to sourceforge repository to confirm that no separate binary was released for CentOS 4, and then proceeded with the upgrade.
Cleaned up the browser cache, closed it, fired it... Voila! Tres tres bien!
I can't thank-you enough. Keep up the amazing work.