I like Quistis. Her personality has a familiar and enjoyable mix of confidence and knowledge, but with shyness and vulnerability too.

My only complaint about her is that the game almost totally ignored her after the first half of disc one. No more major character development, and very little time in the spotlight for her.

Pity, she was the best character in the game, in my opinion. If she'd got as much screen-time as Squall and Rinoa, she could well have been one of the most-memorable and best-developed FF characters of all time.