To date, I've only ever been to 1 "big" outdoor festival, and that was with my wife & kids. It was OK, but a lot of standing around (thank goodness for Go Outdoors £5 folding chairs!). Didn't see many bands through the day, but got to see Wilko (with Norman) and Madness in the evening. The main stage was in a natural amphitheatre, so you can see the stage wherever you were, and not that many folk in front of you.
Thankfully, we were camped in the "Quiet Family" area, but seeing the mess that was left in the normal camping area (tents, sleeping bags, furniture, etc.) on the way out was an eye opener!
I got the impression that the music was just "something that goes on in the background" and almost coincidental.