I am also learning Dutch with Rosetta Stone, and i personally think it's a strange way of teaching. It's hard to pick up because they don't translate anything for you. It's probably just my way of learning but i have been learning for 4 months now and am coming to the end of the 2nd unit out of 3 and i find it really difficult to put a correct and grammatical sentence together. I think i need more practice in conversation.
How do you find it?
I've never used Rosetta Stone, but I get the impression from what people say about it, that the main purpose is to give you a feel for the language, make you familiar with the sounds and turns of phrases, which is obviously more useful for understanding and basic conversation purposes than for writing.
I don't think there's any single learning method, software or in a book or in whatever other way, that will work on its own, though. Each method will have its stronger and weaker points, and the latter will need to be compensated for somehow.