Massive improvement from BES5 and 10. Installation takes minutes. Adding new users almost effortless. Device management allows various options ie: remove only work profile, wipe it all, lock it all. Also finally easy clustering option, can add remove additional BES servers for redundancy with a few clicks.
New bronze, silver and gold licensing model can be a pain. if you need simple user->device bronze is ok. However if you want app control, restriction, collaboration you need to opt-in fro more expensive options.
Also, server very sensitive to Java. It will only work on one or two versions of Java. Not very good if you are trying to stay on top of things with patching out-dated software.
Also isn't compatible with BES5 devices.