I'm such a total lurker, and not a new mom, but this was bumped to the top at the home page and drew my attention so I will respond.
I really like the 30-Day Shred! It is a great well-rounded workout if you are pressed for time, as it implements strength & cardio, and you really can work hard for those 25-30 minutes. I don't consistently do this workout, though - I throw it in once a week, or more, if I don't have time to go out for a run or get to the gym. I feel that it's a great substitute for a long workout! I actually did get to level 3, but after doing it a few times I found 3 was more boring than 1 & 2. So instead of 3, I would do 1 & 2 consecutively for more of a challenge (skipping the cool-down after 1 and the warm up before 2, obviously).
As for results, I feel like it helps me burns calories without a ton of time committment... even though I do prefer more cardio in my workouts (like going for a nice run), it will do in a pinch! Yes, I know I'm weird!!