I'm just finishing the Rocket German Premium (Level 1) course and have found it to be tremendously helpful, and the most motivating foreign language course I've taken.
The most powerful thing about the Rocket German Interactive Audio Courses is that the course focuses on a conversation based narrative and sentences rather than focusing on memorizing words and grammar rules. After three years of High School German, when I went to Germany I found i was unable to construct or even understand sentences in real time and felt hopelessly stupid.
Maybe it is also a critical mass of all the previous study, I've been doing over the last eight months but in the past 26 days of Level 1 Premium sentence work, I seem to have learned enough about the structure of simple sentences that I can understand them and even put together all the conjugations and declensions, dative, and accusative case endings in real time which seems to be producing a positive feedback loop to create a lot of motivation. So I've been able to study at a fairly intensive rate. For example I've eared 82,17 points and nearly finished level 1 in the last 25 days.