COR is a phenomenal job, you will not be disappointed. If BLU didn't exist, I don't think I'd ever play anything but COR.
:p I start my FFXI career as a selfish stinky immortal, until an arrow hit my knee and I discovered what it means to be a pirate: freedom, friendship and gambling for a brighter future.
This job has tons freedom in terms of how to play it, it's all about helping camarades, and it's also about taking risks for the better result. I was deeply obsessed with this job, maybe because it reflected a life that I want irl but unable to accomplish because of responsibility and circumstances.
I'm never a hardcore gamer nor anything close to it, and I never play any MMO longer than 2 months. But in this game I start doing endgame and grind tons of stuff, learn how to make parties and lead people, learned how to create excel to calculate dmg, learn how to min maxing gears just for this job. I can never imagine I would really get into a mmo if COR doesn't exist in this game. There are times that I try to learn and gear another job, they all end up horribly since I quickly lose interest in any other job that I tried.
Like what Oraen said, COR is awesome, and I don't think I can play anything but COR. That probably makes me a horrible player though.