It's definitely a great game. While I prefer VIII, X and VI since all three have better battle systems and soundtracks, IX still has lot's going for it.
Vivi is the most interesting character in the game and probably the best. Beatrix is also great. The story and setting is a good mix of medieval and fantasy. The music, while much weaker than VI, VII, VIII and X, is still good with some amazing tracks like the battle and boss theme's, Melodies of Life, Vamo' Alla Flamenco, Not Alone and The Dark Messenger.
You're in for a fun ride! Enjoy and take your time.