He is a difficult character to like, however, and yet he never passes the line into the utterly dislikable. I think this is due mostly to House himself, who keeps Chase's baser instincts in check by calling Chase on what he does and harassing him endlessly about it. More than that, since House--who acts as the moral center of the show--tolerates Chase, the audience is persuaded to tolerate Chase.
For instance, in the episode where Chase is being questioned for "killing" a patient, House takes a fall. He does it in his usual grumpy, cynical way so at first you don't realized how much House hasn't protected himself. In large part, this is due to House's honest evaluation of his part in the situation--he didn't tell Chase about his father and thus left Chase open to the shock of sudden knowledge--and also to House's leadership style, which is to protect those under him (House's refusal to fire any of his people, not even, at first, Chase, says a great deal about his personality; he would prefer to deal with his interns himself than feed them to the wolves).
A complex, not fully likable yet watchable character is difficult to pull off. I've never been able to get into Everybody Loves Raymond because the characters are SO horrible to each other. They cross the line for me and becomes unbearable. Everyone has different tolerance levels in this regard. I've never cared for meanness as its own excuse, which is, I suppose why Chase remains so remarkable a character to me.