Next to eyes, I think it is THE most important feature on a woman. I do notice how women cut, style, shape, and color their hair.
Personally, I don't like curly or nappy hair - usually straight. As for length, it is usually good at shoulder length, but some people look really good with shorter hair and really good with longer hair. Any color is fine, but I like brunettes.
In general, it depends on the shape of your face. Just because a hair style looks good on some celebrity, does not mean it will look good on you.