Three weeks of learning anything, by any method, isn't really enough to tell how well it's working. You say things like , but you have no way of knowing if that's true or not.
If you have commute time or similar where audio materials are the only thing you can use then sure, Rosetta Stone audio (or JPod101, or whatever) is a helpful supplement. I'm going to suggest that if you just took that one hour you currently spend in the evenings and switch out whatever you're currently doing during that time to using either a physical textbook or a similarly structured online course (e.g. Erin's Challenge or even just working through Tae Kim's grammar website), that you would see faster improvement than via your current method. It's not all or nothing.
What was "Level 4" on the old system (as previously linked to) would now be N5 in the new JLPT.
Test yourself if you like. You are, I suspect, misunderstanding how much is covered under phrases like "basic grammar". Eight months to bring yourself from the start up to N5 level is a quite reasonable timespan - an hour a day spent with a textbook is 200 hours in a bit under 7 months, not counting listening practice on your commute. JPod101 is quite good for that, I would say better than Rosetta Stone as they do explain the grammar they use and it's conversations rather than single phrases - I used to listen to it walking to work and back.
