It's actually 8 days. There is a 3 day pre-cleanse before the "real" cleanse. And yes it works very well! The best Colon Cleanse out there in my opinion.
I have done the 21 day whole body cleanse and I wasn't totally blown away by it. But I am pretty young..so I may not have even needed it. It's not like you see results like you do in the colon cleanse..you know like mucoid plaque. You just take this stuff..and that's it. But I'm sure it helped me. You know, it can't hurt.
Yes, you want to to the Colon Cleanse first. So, before you order anything..decide if you want to do the 21 day cleanse. Because like you said, you get it free. Better to spend $275 than $375, right? ;o)