For Cardio, I am one of those Step Blast and Rhythmic Step gals. I can't pick a favorite from those two.
For upper body strength, I do PUB, and mix in a set or two each of the S&H bi's and tri's. I get a real kick in the muscles by adding a set or two of the S&H in conjunction with PUB.
For lower body strength, I primarily do PLB, but when I have time, I like to add the Lower Body Sculpt from the Body Fusion DVD. This is like the S&H add-on with upper body, and gives my legs that extra kick (no pun intended).
Abs: I have recently discovered the Power Hour abs and REALLY like this ab segment.
Looking forward to my new DVD's, though. Maybe I'll get some new favorites! And based on several other responses, I suppose I'll have to give IMAX 2 a try before long. I've been too hesitant because of my asthma, but if I modify the moves to keep them a little lower intensity for me, then I should be okay.