I'd like to put in a good word for Cardio Classics. I've been using these workouts as my "morning workout" once a week, when I do weight training in the afternoon. I'm not a morning person, and the less complex choreography (though not all simple moves) works great for me! I like the lack of torquey moves (in general). The Cardio Hits workouts contain more ricochets (which I have figured out how to modify for me to a non-torquey move) and flying angels and other 180-degree turn, fast recoil moves that I don't like at all (but, again, I modify them).
I may not the the typical Cathe step exerciser, because I often like athletic moves over complex choreography, and I don't get as bored by the repetitive up-up-down-down type moves at the beginning of Step Jam, for example. I just use this as an opportunity to really hone in on form and posture and range of motion, and I can do these on an 8" step and get good intensity (higher intensity than the non-blast segments of IMAX2 and 3, at times, but lower intensity than the blasts).
And I like the music! I much prefer working out to unrecognizable mostly-instrumental music than top 40 music from any decade (unless it is a soundtrack made up of MY favorite tunes, which will happen only when I make a video, LOL!).
As to your original question: these are less hard to master than subsequent workouts, as some moves are introduced here for the first time and broken down, and Cathe often previews moves before she has you join in (quite a bit different from her current technique). Once you learn the moves, you can join in with her as she previews.
I've been using Cathe's step workouts since Step in Motion 3 (around 1992?), and have found that working through them in order has made each subsequent one easier to catch on to. I think that's still true: I didn't keep Step Blast from the BB series, and there are some moves in Low Max and IMAX3 that were introduced in that workout that would have been easier to catch on to, IMO, if I had done Step Blast more than once!