At the ripe age of 25, I had a colonoscopy. Honestly, the only miserable part was the prep. I had to take a whole bottle of Miralax the day before. Awful!
The procedure itself, the only problem was my high tolerance for the sedatives used. They kept injecting and injecting and nothing. The doctors were amazed by my tolerance. I managed to stay awake during the procedure but was so out of it it didn't bother me (similar to twilight surgery I have had). I actually found it cool to watch the procedure on the tv screen.
Best part, the nice long refreshing nap!