I like him!

In fact Tyrion Lannister is a Lannister to the core. He may be an outcast of them, that why he's gained popularity. But his attitude is in fact not so much better than the rest of the Lannister's. I'd place him as a person somewhere between Jaime and Tywin. I don't have any problem with him, though. He is likable. Fun. (Just for the credit, I do love Lord Tywin, but I don't really like Jaime because of the Bran business, that was extreme)

I think he's as honorable as it's possible for any Lannister to get, but he does posses the same ruthlessness as the rest of his family and will use it when necessary.