I've been using the Transfirmer and the workouts that come with it for several weeks. I really love it, in spite of the weird, Japanese-cartoon name! It's a well-thought-out piece of equipment (for once, the Firm got it right). I wouldn't however, use it for impact step aerobics, as it is a much harder plastic than the Club Step.
The BSS4 workouts are really working my booty well, and the incline of the Transfirmer really hits the glute/hamstring tie-in area really well.