Yes! I've had one, a few years back. My boss found out I was interested in doing herbal detox's so he took me to his Homeopathic clinic and treated me to a colonic (yes, weird, I know...).
So basically you go into the room, and lie down on a padded bed-type thing. Those ones that are in the doctor's office. You have to take off your pants and such, and the "doctor" covers you with a gown. Now.. here is how it goes, because I am an adult, she was about to *insert* the adult sized tube into me, but I am not much into things going up my poop-shoot, so I asked if she had a smaller one, and she did. So she placed a small metal tube about 2 inches long onto a longer set of two tubes coming from the wall. I had to lie on my side, and she put the tube about an inch up my you know what.
Ok, so you just lie there for an hour, on your side, in like a fetal position. The warm spring water will travel up your colon, and back out again through the second tube attached to the metal piece. It's not painful, but a sometimes it feels like some gas, and you even fart a bit! In a metal tube! With a colon full of water! Anyways... too much info?
So.. the after effects. Well, I had to go write an exam right afterwards, and nothing happened ( she warned me that some water can come out afterwards).
But, I felt REALLY hydrated. I felt like I had been drinking nothing but pure water, and because of that, I felt a little more energetic and 'light'. Of course this doesn't last forever, and no weight was lost, but as someone who didn't use to drink alot of water (even though I lived in the desert at the time working horses all day), I felt great.
I liked it, and would do it again, but not rushing back to have someone stick a tube in my bumhole....
So, I thought it was a great start to feeling good, and hydrating your body, which is so important!