I would go ahead and buy it, I think it's a great workout. But, I wouldn't say it's similar to C&W. Similar in format, but Circuit Max (IMO) is WAY more intense than C&W. There are 6 circuits instead of 4 - 2 hi/lo, 1 kickbox, 1 step kickbox, 2 step. For the weight work in CM, it is all compound. This means less focus on upper body than there is on C&W. I usually end up focusing on legs only during Circuit Max. Also there is some good plank work at the end of Circuit Max.
By the way, there is a thread somewhere that discusses the differences between these two workouts - it was going right around the time people were getting their new I-Series videos. That may be of some help to you.