Nice, we were with Heroengine but decided to move on fast as they clearly couldn't handle the project we are building.
It's great for WOW style MMO's which limit your movement direction, also nice for games like Fable. 
Best of luck with it.
We are actually building a completely custom character controller and camera (for play mode).
As for engine quality, the engine is being used for Star Wars The Old Republic MMORPG