Having only attended one Coachella weekend, keep in mind all my opinion is based only on those three days. I did the camping onsite thing and I am not sure if it was just me, but things were so loose that I could have camped for free. Oh well. I never kept anything valuable in my tent, but no one ever messed with it. (I know because I set up things to tell me if there were any intrusions). Seeing a security guard get thrown out by another security guard did not make me feel safe though. Sometimes the bag searches were quick, but often it was thorough enough to be at least a little annoying. Regarding sleep, the music going on in the Dome sometimes even goes past 2 AM and is super loud, no matter how far you are from it. The shower lines were never horrible, but not always worth the wait for me personally.
For the festival itself: Be prepared. Dress appropriately, have earplugs, sunscreen and plenty of water. I am not sure if this was the first time but there was a plastic water bottle that was 10 dollars that could be refilled for free all weekend at a few water stations. A little electric fan would have been nice but is not required for survival. People pass out. A girl did right next to me and she was alone, but luckily security got her out. I wish I had brought a straw hat of some sorts to give me more shade, but I was avoiding trapping heat in the place it escapes the most, but I think I should have made an exception.
Sometimes there are tough choices to make and you will have to miss some or all of a band you like, but this is the least of your worries. There are always interesting things around to see, whether it be art or people. The food is overpriced, but there are some things that are in a relatively decent range. One example is a very large slice of pizza for six dollars. It is everything people say in general: drugs, heat and good music (at one stage if not another). It is an experience, but not for everyone. If you are not sure if it is your thing, going one day might be a safer bet. Just be safe and watch out for snakes on the way out. Almost stepped on one. Also, try parking near an exit if you can and goodluck getting out of there through the insane traffic if you stay all day.