The only really big one I've ever done is Womad (about 8 times now), and I think it's fab. I have without doubt heard some of the best music of my life there. OK, it's all jolly middle class etc, but it's very family friend and mostly tosser free. Toilets are pretty damn good, it's very well organised and the prices are fairly reasonable IMO.
I imagine going to a rawk/indie type festival full of boozed up teens/twenty somethings would be an entirely different kettle of kippers however...