Have you tried posting this on the families board? You might get more responses there.
I don't have one, and after some of the reviews I've read, I don't plan to get them for my kids. I haven't decided exactly what I will get the kids yet, but I'm thinking a cheap HP or Kodak digital that they can share. But my kids are older, 9 and 6, and can use my Cybershot fairly well.
For a 4 year old, I'd recommend the Fisher Price "kid tough" camera. Its the same price as the Disney pix click, and while you'd be giving up the character aspect, I think the durability is worth it! We bought one for DD when she was 3, and it survived being dropped by clumsy little hands and all manner of well-meaning abuse. It also has a SD card slot to allow it to hold more pics, which is a great feature for once your child gets the hang of pointing the camera and starts getting shots worth keeping (or for if they just don't want to review the pics as they go).