In my college, we have a “Language lab”, for which we have to get 16 hours logged throughout the semester for a foreign language class. In it we can watch foreign flicks, do language homework, and use a slightly modified Rosetta Stone (The teachers cherrypick certain exercises to follow their course a bit better).
There is absolutely no way that I could use that Rosetta Stone as my primary source of learning a language. It doesn’t teach you grammar, it doesn’t teach you how to arrive at a sentence, it just says the sentence. It may work for others but that doesn’t work for me, I NEED to know how you get to the end result.
It’s wonderful as a secondary source, to solidify what you’ve learned in class. It was great for practicing pronunciation, and it was wonderful being able to hear a few other native(or, at least, very good) speakers of the language, and it helped boost my vocabulary. But it didn’t teach structure, grammar, etc.