I agree it's a great track but I think the vocal jump-start in Looking For Someone is even better. Especially considering what their experience to that point had been.
I would echo your surprise but with regards Musical Box instead.
I know I'm the one who brought up Moonlit Knight, but I would also have to go with Musical Box as my favorite opening song....possibly my favorite Genesis song of all.
But, Dancing with the Moonlit Knight would be in my top 10 Genesis songs as well.
Never could totally get into Down & Out....I think there's something about the odd rhythm that I could just never wrap my head around.