I've been doing Cathe workouts now for about four months and my experience with Cathe step has been limited to her very most basic dvds: Basic Step, Low Impact Step and Body Fusion (all came in a step set bought at Target, all very basic, all no impact, none typical of what Cathe usually does), followed by LowMax (long, semi-complex choreography, very tough on the heart but easy on the joints), followed by IMAX 3 (which I've nicknamed OHMYGOD 3 for very good reason... complex and VERY high impact. This forum is loaded with comments about IT! Those are barely the tip of the iceberg but until I buy more (which IS in the plan) I can't tell you more from personal experience. However I believe this website offers descriptions, Cathe's paper catalog gives very specific descriptions, and CollageVideo.com is awesome for great customer reviews of many Cathe dvd's (Collage also break all the workouts down into choreography and impact levels - VERY helpful).
Not being a natural Cardio Queen I came to Cathe because she's legendary for her weight training dvds. They are AWESOME. I've never gotten the results I have with anything else I've tried. I strongly recommend them.
Hope I've helped. Anyone else?