Cho Chang is the only character who consistently shows up near the top of both the most hated and most liked Harry Potter characters. She is hated, I suspect, because Harry has a crush on her.
She is liked, again, because Harry has a crush on her. (^.^) Anyway, she is the Ravenclaw Seeker - Harry's opposite on the field, one might say - and a pretty good one. So far, she has made Harry mangle his language ('wangoballwime?'), spill water on himself, and get laughed at by Ron. He asks her to the Yule Ball, but she goes instead with Cedric, who Harry then proceeds to feel jealous of.
I suppose there isn't really much to say about Cho. She does, after all, have only a very minor part in Book 3 and an only slightly more major part in Book 4. What we know of her is mainly how Harry sees her - the dream girl, I suppose, of the series.
And she plays Quidditch. (*Sigh* - Harry).