I discovered Petra Kolber this past year and really enjoy her workouts. I have PK Step, Step Select, Step, Layers and Links, and Ready Step Go and I enjoy all of them. She has a very creative style but not too dancy (like Christi or Seasun) so it only took a couple of tries at most to get all of them. Also her cuing is impeccable so it makes it pretty easy to catch on. I would say that her workouts range from intermediate to intermediate/advanced, but it's easy to bump them up with more impact if you want to go harder.