I've only ever ran C tires, so I can't give you an honest opinion. I think @Chris has run E's then C's, so he might be the best judge.
I have indeed. I've run an E, a D, and a C. It'a a profound difference going from an E to a C, not something to take lightly. Those who drive their TJ mostly on-road should ONLY be running C rated tires if they value ride quality.