The only unpleasant part of my trip to Zion NP was the two 20-something guys in the adjacent campsite. One night they apparently brought a bunch of beer back to camp and proceeded to get plastered. That's not such a big deal, I guess. However, the resulting lack of inhibition brought about hours of very loud and very profane discussion of just about any insipid topic that entered their heads. I was surprised that none of the parents from the adjacent campsites with young kids didn't approach these guys and ask them to either be quieter or clean up their language.
Otherwise, I had a great time as usual.