Here's the article that convinced me to try it after shaking off the Candy Crush demon.
I've now spent about 30 minutes a day for the past month learning languages. Okay, playing/learning languages, but it beats passively listening to Spanish radio. AFAICT you can't do the translations of actual docs on the app but have to go the website - I helped translate one document about renewable energy in Spain, but I'm way too low-level to do anything with the other languages. I just wish they'd add learning non-Indo-European languages from English.
Anyway, for some reason I've been designated brian.schm3 in case anyone else is playing.