I saw this movie with my 2 kids -- ages 3 and 9. Although I can't say I cared for it much, they LOVED it. I've never seen my daughter (the 3 year old) laugh so much or sit so still at a movie.
As a grumpy adult, I couldn't ignore the irrational plot line. My kids could care less, and they adored the clever funny dialogue and the silly slapstick comedy.
I'd strongly recommend that adults stay away. I'd also strongly recommend that anyone with kids go see it.
My rating of 8 is an average. I give it a 4, but both kids give it a 10. That averages out to an 8.