I had a colonoscopy last year. Fortunately negative and diagnosed as IBS.
The actual exam is not bad at all, though I had the sedative, which was quite nice! Just really relaxed.
No pain afterwards,and I was advised not to drive for at least 24 hours. Sedative kicked in at home and I was dead to the world for a good 12 hours.
As others said, by far the worst part was the clean out the day or so before. Having said, the actual action wasn't as bad as the taste of the liquid. It was really really sweet, and made me gag drinking it.
Just get a few books and Internet and sat in the bathroom

. Each dose takes about two hours to work and then it really does just stop, quite suddenly I found.