I think it depends on what you are looking for. I found YZ Total Body Conditioning to be a very beginner level tape, and was disappointed. Yoga for Athletes is good, but I personally just don't care for Rodney Yee. He is wonderful, just doesn't move me I guess.
I have YZ Power Yoga, and it is TOUGH. But that's what I am into, so there you go. I just love, love love this tape.
Catch iYZ on TV if you can, as another has suggested here. Also, Oxygen has a yoga show every morning at 6 am that I just love. I do it about 3 days a week. It is more modern, uses regular upbeat music, and isn't too strenuous. OK for beginners, but he doens't explain anything so you may want to just watch one morning.
I love yoga, there are so many different types out there. Give it a try. One will probably click for you.