Low Max was the first Cathe workout that I ordered, and I fell in love with it. Now that I have had it for a while, I am less enthralled, as it is a bit long, and my heart rate tends to go down when she is teaching the step segments. I throw it into my routine about every two weeks, and it is a good solid workout when you don't want any impact. I always do it on an eight inch step, and my heart rate would barely get up if I did it on six. A very intense, somewhat low impact workout is Charlene Prickett's Crazy for Step, although she does TIFTP (take it from the top?) a bit too much.
I am lucky that my gym has fantastic step instructors, and I take a very difficult double bench step class every Wednesday night. The instructor also changes his routine every week, so it doesn't get boring.