I've always heard that the P&B shakes can actually make people constipated. I've never personally done one, but I am interested in finding out if it works better, worse, or about the same as oxygen colon cleansing.
If people think it works better or about the same, then it might be better to just go buy some cheap psyllium & bentonite, instead of spend $50 on a colon cleansing product.... but that's just me.