I have done 5 or so in various capactities. The worst are the children ones, because in a childrens pageant, you have parents. And parents are a pain in the rear.
True story: Childrens Pageant. a year ago. I am sound designer/operator. We run dress on the talent segment, and a put out a Sure SM58 for the kid doing singing - basically the standard microphone for vocals, used by everyone. The mother threw the biggest hissy fit because her daughter only sang with X mic - which happened to be a $2,000 microphone used for STUDIO RECORDING - and I had to try and explain why A) we were not going to buy a $2,000 microphone just for her, and B) why even if we did have one in stock, we could not use it on stage. The kid was great though, about 8 or 9 and kept rolling her eyes and making funny faces behind her mums back...
Anectdote #2: Stage manager. 18 months ago. Childrens Pageant once again. Cueing entrances of contestants prior to the judging as well as telling the dome operators where they can pick up the entrants from with their spots (because we were running without tech or dress and this order had been decided on 5 minutes before we started). I had a group of parents constantly bitching with me through the entire segmant that I a) gave that girl far too much time out there in the audience's focus or b) did not give their child enough time or c) that I should get the spots to change colour to highlight their daughters dress (etc).
I have always found the younger contenstants are great, but have always hated the parents. Older pageants, you get your divas, and you get your good ones, just like any show. And co-ordiantors are as a general rule always a pain in the rear - it is part of their job description I am sure.