I’ve just finished week 11 of the 12 week program. I’ve used squats, decline bench, and deadlifts as my 3 core exercises (performed on Monday, Wednesday, and Friday, respectively) and altered some of the circuit lifts each time around (for example, I substituted unilateral leg press for step-ups, swiss ball crunches for incline situps, etc.). On a scale of 1 to 10, I’d give the routine about a 6.5. Overall I’ve gotten stronger, but I don’t feel like low volume per bodypart combined with high total volume per workout is necessarily the best way to go - in other words, I never felt like any individual muscle group got that great a workout, and yet I felt systemically overtrained all the time. I’ve gotten much better results with Ian King’s stuff (well, his leg training series anyway). But good luck!