Becuase bodypump is nearly aerobic, it is completely different from classic resistance training. You fatigue yourself and your muscles through high repetion and quick motion rather than progressive overload. They are great combined, but do give your muscles some recover time. Depending on your goals, bodypump mayy or may not be the right place. If you are already doing cardio and weight training, it's really just a little of each, choreographed. You won't get the full benefits of progressive weight training, but it is fun if you enjoy group exercise.
If you are already fit, it's probably not going to be a plateau buster other than the fact that you are getting MORE exercise. But if you enjoy it, it's great!
Don't forget to rest sometimes
Mel