This has got to be one of my favorite episodes of HnG.
Let's see...
+ Hina-Ayumu scenes. OH GOD HINA IS SO MOE.
+ Sakuya. She's just awesome.
+ A-tan flashback. I think Ayako Kawasumi is a perfect fit to her.
+ Nice distribution of focus between the Hina/Ayumu scenes and the Nagi bit
+ Great animation
+ Hina singing that Dango song. oh wow.
+ As mentioned, some of potential plot points were brought up
+ Hayate reusing Wataru's joke. Surprised that Sakuya didn't harisen him.
+ Using this ep to effectively wrap up this awesome season of Hayate.
- Disturbing lack of Izumi, Miki and Risa.
9/10
I'm expecting a new season in 6 months time. I hope I'm right.