Well, they're fairly useless on their own, it's mostly using them in conjunction with other methods of learning (i.e. a good textbook or two, a few movies, podcasts, games, talking to native speakers) that makes them helpful because you get a little practice where you might not otherwise.
Not sure if the quality of these language learning tools depend on the language being taught and perhaps with individual learning preferences as well. I thought Pimsleur for Mandarin was acceptable and similar to the texts I was using, and since I had the most trouble listening and speaking Mandarin (as opposed to reading/writing), it was helpful to me. But again, disclosure: most of the language programs and resources I've tried were free through school, which was immensely helpful in deciding what I liked and didn't like. I'm not entirely sure I'd buy Pimsleur either ;)
Not sure if the quality of these language learning tools depend on the language being taught and perhaps with individual learning preferences as well. I thought Pimsleur for Mandarin was acceptable and similar to the texts I was using, and since I had the most trouble listening and speaking Mandarin (as opposed to reading/writing), it was helpful to me. But again, disclosure: most of the language programs and resources I've tried were free through school, which was immensely helpful in deciding what I liked and didn't like. I'm not entirely sure I'd buy Pimsleur either ;)