FWIW, I'm quite happy with my N360, after having owned several Nexus and Alfine hubs. The Alfine units are great, too, but I needed something I could reliably use offroad.
I commuted with my N360 last Spring, and felt that it ran fine (to my legs). The only place I notice a loss of efficiency is in the absolute bottom of the range (steep climbs), but even then, it is not too bad.

Good luck with it! It might be worth checking in with Nuvinci to see if you have a faulty unit.