[Xentron]

Having actually used rosetta stone myself for more than a mere 30 minutes I can vouch for it's usefulness.
Of course you shouldn't just use one learning method, combine it with a few others!
Rosetta stone V3 teaches you a whole lot of vocab, pronunciation and teaches you how to read hiragana, katakana and basic kanji.
Of course it's all up till a certain basic level but it really helps a whole lot.

I combined it with pimsleurs and with a few books.
Rosetta doesn't cover the grammar at all as it just reads up sentences and leaves you to figure out how it works.
Just supplement that with a book on grammar and you're set.

Of course the price tag could be a tad much for students but I say the price is well worth it.
I'm not too sure about the online rosetta though... having seen the price I'll probably just try out the trial and leave it at that.