Rosetta Stone offers the user the chance to learn languages intuitively and instinctively. It's an easy and fun program to use. I do feel like it helped me improve my Japanese, especially my listening ability. There are, however, some major issues.
Firstly, the program does not offer direct translations along the way. This might not be a problem when learning a European language, but in the case of learning Japanese, where the structure of a sentence is so radically different, it can be confusing as RS offers hardly any clue to some differences in language that would be tough to work out through intuition alone. For instance, in Japanese there are two different words, 'imasu' and 'arimasu', used in a sentence to refer to things that are living and non-living respectively. The only way I managed to work out how to do the exercise in question was by googling the answer. I probably could have worked out how to complete it, but not with total confidence as to what the words really meant.
Another issue is the writing section. I'm sure it'd be fine for languages based in the roman alphabet, but it's not at all effective for learning Japanese characters. The user is expected to enter their answer only phonetically, and while it's no doubt difficult to enter Japanese characters via a keyboard, I do think the developers were somewhat lazy in not devising a different/better system for learning other alphabets.
Finally, the price: way too expensive. I'll leave it at that.