Cleaning out the crap

Has anyone ever tried colon cleansing? I know there is a bunch of holistic types out there. Supposedly it will get rid of fatigue and low energy. I don't know that I believe the weight loss claim though. By the time the waste has reached your colon, all of the nutrients and calories have already been taken out. So there isn't really any way to lose weight there. So, speak up. What is the best colon cleanse routine you have done? How did it make you feel? Would you use it again?