Tatl was a brat. But she fit into the whole tsundere female character Nintendo has taken a liking to when it comes to TLoZ (Tatl, Tetra, Midna). She had a little bit of a story, though it wasn't all that interesting. I liked her little brother, Tael, much more, but it was good to see that she was protective of him.
She starts out snotty and eventually warms up to Link and deals with her own faults... it wasn't too bad. I mean, she provided some character development, backstory, and interaction without stealing the spotlight from our hero, Link.
I didn't like her personality.... but, I did like the way she was used in Majora's Mask. So, I'm just going to split it right down the middle and give her a five. I've seen better, and I've seen worse.