I'm a language teacher and I've sampled several of the Pimsleur basic courses. I've concluded that they're great IF: 1. You're a beginner in the language. If you already know the basics, the leisurely pace and frequent repetition will drive you up the wall. But for a novice, that's just what you need. 2. There aren't any subtle phonetic distinctions in the language itself that need to be explained in writing beforehand. For example, in the Cantonese tape, the word for "you" sounded like "lay" when the female speaker said it and "nay" when the male spoke. This needed to be explained. Fortunately, the Japanese pronunciation is clear and simple throughout. 3. You want a tape that you can listen to while driving or walking. These are perfect for that.
So far, I've found the Japanese tape to be the pick of the litter, followed by Swiss German, Haitian Creole, and Western Armenian. I couldn't stand more than a few minutes of German and Spanish, which I already know, but for someone else, they might be just the ticket.
Again, if you want a good place to start with Japanese, Pimsleur makes it a walk in the park.