i was recently upgrade to pro version of virtualmin.
problem i found after upgrade is the virtual servers created before upgrading to pro seems to have odd behaviour.
the most common behaviour is when i applied some changes in the virtualserver configuration, it took very long time (5-15 minutes) to finish. more apparent when changing network based setting such as domain name, apache, ip, etc
the virtual servers created after upgrade does not have this behaviour.
some settings also not shown in pre-upgrade virtual servers.