I love that it's challenging at your own comfort level. It's not so much rep or weight oriented but by getting your HR into a certain level. Each individual will do the same exercises, but at their own comfort/fitness levels. I feel that is an extremely successful approach.
I like that the workout is always different so you never get bored, it's guided so you don't have to figure out what to do but can instead focus on form & improvement, and I love that it's gotten me results!! It's the first time I've actually enjoyed and looked forward to exercise even though it's always a challenging workout! And our trainers at OTF Grand Rapids are just the BEST!!