There are few problems with our 5.5 RPM packages
- some (not all) cnf files are silently overwritten on upgrade
- post-uninstall script is missing
- post-install script determines the datadir incorrectly (not considering all my.cnf groups and not handling relative paths)
- post-install script install new db files, even if the data directory from the previous installation exists
additionally mysqld reports that datadir has no default value, which is incorrect.