Wow. So many pages!
So Pinkie was absolutely priceless in her Scootaloo costume, Pipsqueak is all kinds of d'aw, and Shadowbolt Dash was also good for a laugh. So many of the background costumes were also a treat. I really liked Berry Punch's explorer costume. Didn't notice Colgate as a dentist at first, but that's amazing.
As for Luna, like many of you, I'm glad they chose a fitting characterization that covered the 1000 year banishment. Olde speech didn't immediately come to mind, but it really worked. Especially when she used her stadium voice. I think a lot of the disappointment with her story's end comes from our own desire to see the "having fun" situation be the end, but it's great she managed to fit in her own strange way.
Also, we got more Zecora! And she volunteers every year to be scary!
There's only a couple things that needed to be remedied, in my opinion:
1. No Rarity! More than anything, it's the fact she's a fashion designer. It just makes sense for her out of everypony to be involved with the costume aspect of this holiday. Oh well, future plot maybe.
2. No song! Since it's a big social event, Nightmare Night seemed to beg for its own song. The fact we haven't gotten a song 4 episodes in doesn't help either.