We did the Social in April 2002 and had a blast. Three adults and two children, ages 2 and 8. We were the only family there doing the social so my kids got a ton of character interaction. Disney doesn't really advertise this, so I think it is usually uncrowded. Chip played keep-away with my sons autograph book, Pluto licked my children (and the camcorder lens), and they all played games with my 2 year old as well.
As we finished up and were leaving, Mickey grabbed my daughter, the 2 yr. old, and skipped her through the restaurant. Then he proceeded to get down on one knee and sign that he was crying, very sad, and that he loved her and my son. He hugged us all and shook our hands as we left, still signing tears falling from his eyes. It was wonderful, and even my somewhat hard-to-impress father talked about this meal the entire rest of our trip.
And no surprise, we are doing it again in August. This time with ten family members in tow, only two of whom are kids (4 and 10 this time around.
We give it a big thumbs up!