Incredible stuff.
Loved every second of it.
The subtle throwback jokes were too many to name (too bad the majority of the audience didn't get the references since , ya know, they weren't born yet.)
Like Bruiser said the lack of the secondary characters was suprising, especially Mr. Burns.
They made the right decision to go with a straight forward, albeit amped up, Simpson story instead of going the wacky route and having tons of pointless celebrity cameos (which I thought they would do from the beginning)