I did it but I'm not sure it was worth it. When you buy the movies to complete your commitment, you are paying the highest price for that movie. I see way better deals on these movies all the time.
I'm done with my commitment and don't plan on buying anything else...now I just have to figure out how to quit so that I can stop having to respond to their montly selection every month.
If I were thinking about doing it again, I wouldn't.