The procedure was a piece of cake. As the standard is where I'm from (Norway), I was only administered some sedatives - but honestly I couldn't feel much difference. I watched the procedure on the screen, which was quite fascinating.
The worst part, by far, was the emptying / prepping. A month prior to the colonoscopy I took a stool sample (negative for blood), but my doc wanted to be safe.
In the end they nothing was found, not even polyps.
EDIT: I had put of going to it for the longest time, but a friend of mine (35 years old) was diagnosed with stage 4 last year, which pushed me to get it checked out. He had experienced prolonged constipation, that's it. When the tumor was found, the cancer had spread to both of his lungs and liver. He's still alive, and fighting it.