Unless you're paying per class I don't think it would be a waste if you don't like it. Do you mean like a yoga body flow? I just did an astanga body flow and it was great! I'm a big proponent of trying new classes. You never know what you'll love! Plus everyone's classes and experiences are different so go for it!
If you are referring to the Les Mills Body Flow, I've tried it. It's a good workout - similar to a vinyasa yoga class. It's basically a yoga fusion class that is set to music with a routine sequence of moves.
Did you go? What'd you think? If you WERE talking about the Les Mills version, I used to go very often and found that my experiences always varied greatly by the instructor. There were a few I loved an a few I couldn't stand. For a while, my gym offered a Sunday afternoon pump/flow combo that was an awesome way to end (start?) the week.
'Life should not be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather, to skid in sideways, chocolate in one hand, wine in the other, body thoroughly used up, totally worn out, screaming 'Woohoo! What a ride!' So every day is a holiday and every meal a feast."