The change leadership feature was a *huge* improvement. It also helped when you wanted to "over-ride" what the computer would automatically do action wise. And then, of course, to use the special one-time-in-battle only move for Serah & Noel.

As per the monster teammate thing, I thought that it was an innovative way to have only 2 "playable" characters. But much like you, I pretty much stayed with a few monsters. I didn't farm materials to upgrade them, and Chocolina (who I predict would be a huge hit at ComiCon).

I had CaitSith (as my medic).
I had a Blue Chocobo (as my reaver).
I had a robo-type monster (as my sentinal).

Other then that, I just kinda didn't care.
~Jeordam