My team and I have been blown away by the engine, but there are times when things are not trivial. Given the recent release of the VR Editor, and plugins like Unreal.JS and sphinx.UE4 we are now proceeding with integtrating Lucida into the UE4 Editor. Lucida is a personal assistant similar to siri - but open source, one developed by the University of Michigan and Clarity Lab.
http://sirius.clarity-lab.org/
Could you provide any feedback on this initiative?