We are a couple of adults and did 3 character meals last year. I don't ask much from a character meal. As others have said: stop by, give a hug, pose for a picture and move on. Pooh & friends at Crystal Palace were very fun. Cinderella, Snow White, Prince, Charming, and Suzie & Perla at 1900 Park Fare were all fantastic, stopping by mulitiple times and taking time to chat a bit as well. By now we were really getting into character dining... Then we went for breakfast at CRT. Before we had even sat down Belle, Aurora, and Fairy Godmother and all rushed by allowing us barely to even snap a piture before they moved on. Mary Poppins acted annoyed by the fact that we even wanted a picture of her. The only bright moment was Snow White... which turned out to be the same Snow White we had seen at 1900 Park Fare... she was great once again! She mentioned that she was glad to see us again and posed for more pictures and was just perfect.
So to summarize... "good" character interaction for me is each characters takes the time to stop by for a wave, a hug, a picture, and maybe a moment of interaction. That's all I need.
"Bad" character interaction is when each character seems annoyed by having to stop by your table and seem to try to get away as soon as possible. While we enjoyed eating in the castle, we do not plan to go back.