I was actually a little bit dissapointed, I took my younger brother on its opening day, he enjoyed it the whole way through but I have to say I got a little bit bored after the first half an hour.
The first half an hour was fantastic, it had the right gags to plot ratio, but after that it got a little too plot heavy for me (yes I do realise I am talking about The Simpsons), which wouldn't have bothered me if there had been more jokes.
Another gripe I had was not enough Bart and Lisa, Lisa was hardly in it atall. It sorta reminded me of Shrek 3, were Puss and Donkey were secondry characters in it.

Overall I'd give it three stars, definately worth going watching at the cinema but I doubt I'll be buying it on DVD.