What is the ideal age to visit a Disney Park?

9ish - Still at the edge of naivete and tall enough to ride all the rides.

Early 20's (without kids) - Able to appreciate all the subtle details as an adult without all the "baggage." ;-)

Or add your own ideal age.

30's (with kids) - You can appreciate all the things for adults, but really enjoy watching your son(s)/daughter(s).

Any age! Even if you can't remember the expereinces, going to Disney even at a young age you have the photos.

5-6 - Old enough to understand what's going on and at the peak of soaking up all the magic!