People i know who have had their bowels looked at say the worst part is drinking gallons of pink stuff the day before. i think they did it to me down the throat ages ago to check out possible ulcers (there were none) and the worst part was a sore throat. It's probably much better now.

My partner's had it done several times in the last eight years or so (esophagus issues), and he says there's absolutely nothing to it.

I had it done a couple of months ago. There isn't much prep for (upper gi) endoscopy apart from not eating the morning of. You may have a bit of a sore throat afterwards. Take a water bottle or other drink so you can get lots of liquid in there after it's done. The drug they use (propofol) is fun!

I had one done about 15 years ago to check my esophagus (I had reflux really bad, and an ulcer, and they took a tissue sample for biopsy) and there was nothing to it, not even a sore throat. I was under conscious sedation (demerol and versed), and all I remember about the process was the nurse getting excited to see me have a reflux during the actual procedure...she'd never seen one real-time. She was surprised I remembered that, but there was nothing else of note about it.

Had one (upper) not long ago. Like gaspode says, it doesn't hurt at all - I was asleep before they had all the drugs on board and woke up none the wiser - but expect a sore throat after. I stuck to soft food for about 3 days after.

My mom has done it twice and the hardest part is that stuff you have to drink. She kind of liked it though (not the taste) as the second time around she was on some three day strict "drink this at X and that at Y hour" routine and she felt great afterward, like she had done a proper fasting.
The whole camera sent down throat routine is uncomfortable at best but it doesn't hurt. She was not asleep or sedated when it was done but they do that for people who request it (in sweden) since the gag reflex is pretty strong. My mom just had some really minor local anastesia(sp?) thingie for some reason I don't recall. She needed to be awake is all I know.

Related: How do they move the tip of the endoscope around when it's inside you?

The little people who live inside you move it around on command.

Ok. Thanks for the reassurement y'all....

The little people who live inside you move it around on command.

What?!?!? Maybe they can find that penny I swallowed when I was 5. I never saw it again.