I am not Cathe but I can explain the pyramid system a little.
Joyce Vedral. uses it - she uses the half pyramid and the full and goes from lightest up: for example - if you were doing a half pyramid for bicep curl - you would do 12 reps with your lightest weight, 10 reps with your medium weight and 8 reps with your heaviest. That is a simplistic explanation. The full pyramid as Joyce does it is - 12 reps with your lightest, 10 reps with your medium, 8 with heaviest, then do 10 with medium weight and 12 with lightest.
As far as the Joyce V. programs - her programs that are designed for strength use the half pyrmaid up and superset between body parts. Her program that uses the full pyrmaid system is IMHO designed for endurance and she designed it for definition.
I can't wait for Cathe's pyramid tape - I get great results from the pyramid system and I love, love, love, Cathe!