Trixie is super egotistical and rude, generally just looks down on everyone, and tends to torment Twilight for her own amusement. -3-' And what kills me is she never seems to learn her lesson. She just keeps going back to being the same old pony.
I think almost every character has quite a few people liking and disliking them. I understand why the character of Trixie wouldn't appeal to some people, though I think she's great. And powerful.