This is a minimal upgrade. The main task was upgrading the KVM OS from Ubuntu 12.04 to 14.04.2, which went smoothly. Some base applications have been significantly upgraded but, thankfully, the mail stuff (postfix/dovecot) came back up immediately. The apache config files needed to be re-configured but not significantly. There is a migration document from 2.2 to 2.4 for pointers. The python libraries had a little hiccup due to a nice little new utility called virtualenv that replaces the old handcopy of pointers to the desired python version and libraries to use.
There are no specific improvements in this release, just an OS upgrade.