I have to agree with Xanatos because Blue Magic users are some of the best and strongest party members in my groups. Kimahri was in fact one of the worst Blue Mages but the other two that I've played with, those two being Quistis and Quina, funny that they both have names starting with a Q, are fantastic.

If I didn't have Quina in the game with his/her Limit Glove during my level one playthrough all would have been lost. Plus s/he is also capable of things like Lv. 5 Death which makes taking down the Grand Dragons all too easy and Auto-Life that was essential in getting through the three required fights in Pandemonium on Terra. Quistis was also one of my favorite characters in FFVIII, I can't remember the exact limit move but one of her limits banishes all the enemies to some other dimension and it's an automatic win and easy EXP. She also was a great help with Ultima Weapon, Omega Weapon, and Ultimecia. Love a good Blue Mage.