I'd use it as a cardio workout, however with using 1 lb weights I can see how your upper body would get worked, so I probably wont use it after an upper body day until I get in better shape! I dont really think it would qualify as a circuit workout, it's really primarily cardio with the hand weights used to up the intensity.
I also did Powerstrike 5 the other day....I loved that workout too!
I previewed Bodystrikes and that looks like a great, standing, non-weighted lower body workout.
I also previewed KCM's Cardio Kick Step-Boxing. It looks really good too and can be split into 2 separate cardio workouts if you dont want to do the entire 85 min workout (that time includes abs as well as warmup and cooldown).
So many workouts, so little time. I got 8 new workouts for Xmas plus I pre-ordered STS.