I just got their mandarin CD. I listened to it for a little bit and it sounds that is a great method. I got it so we can play it for our baby before she goes to bed. I'm also planning in getting the mandarin little pim. So, to answer your questions so far I think it was worth it.
Now, as a native spanish speaker I can say that with spanish may be a little bit easier to learn because the phonetics are always the same, so if you decide to use dictionary may not be as bad. Just a thought.