This time, it's her story.
The new combat system revolves around dresspheres. With dresspheres there is no real need for Aeons anymore.
The dresspheres include:
Gunner
Thief
gun mage
warrior
alchemist
samurai
dark knight
berserker
songstress
black mage
white mage
lady luck
trainer
mascot
special dresspheres:
yuna - floral fallal
rikku - machina maw
paine - full throttle
The storyline is not exactly new since it's based off of its prequel, and a side story for Auron might have been preferred for some, but I still at least enjoyed the Lenne/Shuyin 1000 year old Machina War well enough. The ever improved graphic design is breathtaking, and the music is beautiful. If you are looking for the answers to FFX, then pick up the conclusion story to it, FFX-2.