It's both a family movie, and a dark movie; funny and touching at the same time.
With three kids, a loving wife and a kingdom on his side, Shrek feels stuck in a rut. He makes a deal with Rumplestiltskin to have one day of his old life terrorizing the townspeople. In return, Rumpy gets one of his.
Much of the plot is predictable, but works anyway. SFA falls somewhere in the realm of Back To The Future II's bleak present and the immediacy of 24 all within the Shrek universe's blending of fairy tales and modern pop culture.
I saw it at Southdale in "An IMAX 3D Experience". Neither Carole (who also loved the movie) nor I thought the IMAX part was worth the extra price, thought the large screen was nice, and the 3D was used effectively but not required for enjoyment.
You don't have to stay; there is nothing after the credits.
Highly recommended if you liked the other three. Possibly the best of the bunch.