I really enjoyed the way they wrapped it up --Mysterion/Kenny actually got even better (especially the bits with the pistol). I liked the surprise hero at the end.
I'm also happy they totally dropped Captain Hindsight.
This episode didn't feel padded to me, rather that they realized what the best parts of the story were and opted to just stick to those.
"I'm going to bed..."
Also, I recognized the kitty bit, but I couldn't remember which cartoon it was originally from --anyone remember?
Is this the first season we've heard Kenny's non-muffled voice?
Other than the movie, I think you're right --unless, of course, you count the first Mysterion/Coon episode.
Incidentally, the tied an older explanation of Kenny to this one.