I fell into serious FOMO b/c of some friends joking around about the owl harassing them and then getting into daily xp competitions... so I joined and tried Klingon.
It is very not good. The sentences it builds for learning are...weird at best, and the audio was inconsistent. Maybe it's my learning style conflicting with how Duo does things, but... I hated it.
Duolingo is not so much about teaching, but more about (here it comes again) building engagement with the users. It didn't start out like this, but somewhere the MBA's probably took over.