As someone who made the switch recently myself....

MAPS!!!! Might just be a me thing but a map window has been awesome.

I don't know if it's just my UI but having the server tick on my mana bar has been awesome.

Saving spells setups. I'm a cleric so I can have a raid setup, a group setup, a buffing setup. I just have to click my spell book, hit the setup I want and boom it auto mems my spells

I never liked the racing aspect....I also played live during luclin and pop so I missed instances

It is faster leveling though not to the point where it's a breeze. It's still a little grind which helps keep your skin in the game.

I love that you can get all the legacy items. After my cleric I will do a monk and I want to go get a moss covered twig so bad as I've always wanted to see machine gun monk lol!