I hardly ever use most of them, since I have so many workouts overall, as well as most of Cathe's (I did at one point own all of Cathe's workouts from Step 'n Motion 3 on, except for the Intensity Series compilation DVD, but got rid of some along the way).
There are a few that I've used a lot, more that I use less often, a smaller group that I use even less often, and one (Timesaver)that I've never used (and should either use or get rid of!). I haven't even done the entire Drill Max workout (I've done premixes and the segment on Cardio Fusion), or LIS and Boot Camp from 4DS yet!
Some of the workouts I rarely do are actually really good workouts (some, like Circuit Max, I used to do A LOT when I first got them), and when I go back to them, I think, 'wow, why haven't I done this one for a while?" I 'rediscovered" BMax (the original) and PS in the last year, and they were very nice rediscoveries!