Sorry, bit late to this discussion. Took me a while to read through all of it. I think there is no one system that can teach languages fluently. As a language learner, I currently use a variety of ways - from speaking to native speakers, watching movies, using flashcards, playing games and listening to podcasts.

I'm also the founder of language startup called http://www.nativetongue.com If you are interested check us out. We combine language learning with gaming, to make it fun and addictive. We have the following apps available:

- Learn Chinese with Mandarin Madness http://itunes.apple.com/app/mandarin-madness/id494800742

- Learn Spanish with Spanish Smash https://itunes.apple.com/us/app/learn-spanish-spanish-smash/...

I think the ultimate would be learning like Neo in Matrix. Just plug a cord into the back of your head and upload the mandarin lesson module, and absorb it in seconds!