I "kinda, sorta, sometimes" use rotations ;-) , and I've been more into them after using P90X and seeing how effective a well-thought-out rotation can be.
Sometimes, I will set up my basic rotation around a weight workout series (the Pyramids or GS, for example), and fill in the cardio days less formally (setting up specific weight workouts on specific days, but setting up "types" of cardio on other days, and choosing the actual workout the day of or maybe the day before).
Usually, I still go pretty much rotation-less, but I have a general plan (doing one interval step workout during the week, alternating between upper body and lower body focus--in cardio as well as weights, such as doing boxing or kickboxing wearing weighted gloves on an "upper-body cardio" day).
When I have a hard time getting in workouts, I just plan the workouts I can get in based on what I need at the time. For exemple, if I haven't gotten either cardio or weights for a while, I'll do a combo workout. If I need lower body focus, I'll do a lower body workout (nowdays, often preceded by a short cardio workout as an extended warm-up and metabolism booster).
I think rotations work well because they help you make sure you get everything in during a certain time period.
I've never done a Cathe rotation, but make up my own (some of the rotations I've looked at, and they weren't many, had a weight workout followed the next day by a circuit weight/cardio workout, something that I don't find effective).
