The Rocket Chinese course is comprehensive and contains a good variety of tools. There are a couple negatives though. The main one is that the male voice actor's pronunciation is not very good. That's a huge drawback when you're trying to learn to pronounce a language correctly. Offline use on Android is fairly minimal. It's painful to enter pinyin for exercises that use it, for instance you can't just enter dan1cheng2, you need to find a way to enter dānchéng. Some odd vocabulary items are introduced early, like "go dutch" or "seat belts". It would be nice to have some additional drills and reading material. Overall though, if they could replace the male voice (or he could improve his pronunciation and cadence) it would be a very good course. (I haven't used their customer service so I'm giving the benefit of the doubt with 5 stars.)