On our Fantasy cruise last April, DD went on our first full day (Sunday), spent about 2 hours in there and decided it was not fun. She went back a couple of days later for the science projects and thought that was ok. On Tuesday, she went for the Pluto Pajama Party and was hooked at that point. Couldn't get her out of there after that. She really enjoyed the computers in the Tinkerbell area where she could make her own fairies and print them out. She enjoyed the magic game floor and some of the stuff they did there.
Some of it, I think, is the social interaction with kids her age and not being with the 'rents the whole time. She would run into other kids she met in the club at various places on the ship and she loved that.
I do think it's an individual kid thing. I honestly thought after the first day, I'd never get her back in there. Then after day 3, I didn't think I'd get her back!!