I haven't learnt Japanese (besides a few basic phrases that keep popping up in anime), but I do have a bit of language learning experience (more than most native English speakers, at any rate).
If you want to learn a language without going to a class or a place where it is spoken, you need to put in a lot of effort. Whatsmore, you must always try to read and listen to material that was aimed at native speakers, because stuff aimed at learners usually has simple vocabulary and sentence structure, and is more carefully pronounced than it would be in a normal conversation. Trying to learn by following a single self-contained course such as can often be found in language learning software usually won't work very well, unless you only want to learn the basics of the language (and I can't see why someone would only want to learn the basics of Japanese).
