I think she's definitely gotten better with time. But I never hated her.
I never got the bad hair thing, but I'm beginning to think I never get the bad hair thing.
I don't remember if I really hated her in the beginning or was just, meh. I re-watched the pilot the other night and I was struck by her bad hair and stiffness. I suspect the stiffness might have been in the script. (To play against Castle's free-spirited-signing-of-boobs-ness.)
I was aghast at her hair though. It was short and looked, at times, as if they'd plastered it down on her head with an entire tube of product.
ETA: The hair could have also been intended to help establish character. NF seemed to walk around the entire pilot looking like he just stumbled out of bed still wearing his clothes from the night before.