I started with Jillian's 30 Day Shred because it was mentioned all over the place online. (Great workout, and especially good for fitting in to a busy schedule because it's only ~20 minutes.) I chose to try BFBM next, and I'm very happy that I did. It's a fantastic workout that really got me sweating.
It's about 40 minutes (twice as long as 30DS) and broken into seven different circuits. Unlike 30DS, there are no handweights needed, and there is only one circuit on the floor (yoga mat), so if you need a routine that's highly portable, this might be the one for you. (You can easily skip the floor circuit if necessary.)
Since the circuits are pretty short, the time goes by quickly, and you'll be at circuit seven in no time. There's a fun mixture of cardio, kick-boxing, and plyometric moves to keep it interesting.
Jillian's enthusiasm and encouragement helped keep me going. With two assistants, she always shows beginner and more advanced moves, so I think this DVD would work for just about everyone.
I highly recommend it. :)