Ohohoh, I was so unimpressed with RosettaStone. To be fair, I didn't use it a whole lot but I got to try it for free at the Maxwell-Gunter AFB library (I'm in the Air Force) and I thought it totally sucked. They just flash words and pictures at you, that's it- that'll be $500 thankyouvrymuch. Rosetta Stone tries to pass this off with the reasoning that they are trying to give you the "full immersion" effect- no one explained to you when you were a baby what a noun was and how to use it in a sentence. But you're not a baby anymore. You're an adult- or at least possibly near being one. You can't and don't just sit around for hours hearing people talk to you, about you, and around you. Your entire life can't be devoted to just listening and watching. You've got your daily life to tend to. And plopping your butt down in front of a computer for a few hours a week is not immersing yourself in a damn thing. (Although, if you're really sold on the whole 'full immersion' idea, you can always make a time-machine, travel back to the 1940's and become a Japanese POW in WWII
)
I think RosettaStone may work for Western European languages, but not for Eastern ones and certainly not for Japanese. The grammatical systems are too different for you to easily pick them out without explaination- and why would you want to try and figure it out when you could save a buttload of time and frustration by just
reading a grammatical explaination from a good ol' fashioned textbook?
I know that everyone learns differently and everything and RosettaStone may have some merit but I really don't think it's worth the outrageous price. I think "My Japanese Coach" for the DS (athough this too has poor grammatical explainations) is way better the RosettaStone and it's only $30. Hell, I think Japaneseclass.jp is better and they're free!
But I might be biased, I tried a lot of different products and I always really hated the so-called 'immersion' programs. I find them ineffective, frustrating and a waste of time, and supposedly my brain is supposed to be really good at picking up foreign languages! (Both my mom and I scored perfect on the DLAB) Btw, I thought that Pimsluer (audio course) sucked too. The best audio course is Michel Thomas IMO, they're the only audio course that gives decent, fairly thorough grammar explainations. The MT 'advanced' (although really not not very advanced at all) course goes all the way to -tari forms, and although it won't make you fluent, it will get you off to a great start. And Living Langages "Utimate Japanese' book and audio course was the first Japanese learning course I bought and I still use it all the time (although it's not without flaws, it uses too much romaji etc).
Sorry for the tl;dr, I'm just really against RS as even if you bought everything I mentioned it would still be cheaper than the first level of RS