I didn't know about the changes to the battle system until I actually played it. It took me by complete surprise. I never played FF11 because I'm not interested in online games. (Tangent: I believe they should have just called it Final Fantasy Online, and numbered FF12 and FF11.) Took me a little while to get used to the new battle system and gameplay. When I started, I wasn't too sure about it, but now I actually prefer it over the "traditional" battle scenes.
I have my party divided into two groups.
Balthier / Basch / Ashe
Vaan / Fran / Penelo
As one group gains a level, I switch to the second group, which keeps them leveling up evenly. Currently, they are levels 61/60. Vaan and Basch I try to make my heavy hitters with the powerful armor, one-handed weapons, and shields, while Ashe and Penelo are my primary spellcasters (they have the light armor that raises their magic attack and defense). Although with each having their license board maxed out there really isn't much of a difference in fighting styles or spell casting ability.
If I had to find something that I don't like about FF12, it would be the license board. In other FF games, each character had a particular skill that they excelled in, and weapons and armor associated with it. It forced you to think more about how to balance your party. Early in the game, I tried to keep to that as much as possible, but it became a moot point once the license board was complete. It still vary the weapons and armor, but it isn't the same. Despite that, I still think it is an excellent game.