I'd say it depends on the level of mixing of animal and human traits.
I don't know the word for them, but those animal costumes that consist of latex prosthetics and makeup tend to creep me out because they come off looking like a screwed up human, rather than with a fursuit, where it more comes off as a person in an animal costume.
Also, in anthro art, if one body part is more human or animal than the rest, it tends to be creepy. I recall seeing this one picture of an anthro cat where the character looked pretty human for the most part, but had very realistic, cat-like eyes and paws instead of feet and hands. In a similar vein, a picture of a mostly feral looking dog with human hands creeped the hell out of me.