Hmm.
Well, It's certainly good - and a LOT better than any of the recent series. But its not great by any means, compared to (for example South Park Movie, or Team America)...
but Its nice to get the original characters back - the new Homer who seems to have had a stroke in the new series is horrible, but in the film he's normal again.
I'd give it 7/10. With some real Laugh out loud moments!