I generally avoid ranked for a few weeks after a new champ release just in case the new champ is OP in some manner (as is often the case), and generally hope they're banned if I do play rank. I don't want people on my team playing the new champ because it's new and they probably don't know how tot play them very well, and I don't want people on the opposing team to play them in case they're OP enough that the lack of experience doesn't matter. (I avoid ranked entirely soon after new champs are released since there's not enough bans to go around, and banning the new champ means other stuff gets through.)
In normals, spam the new champ away. I'm happy to learn to play with/against the new champ until such time as I'm comfortable dealing with him in ranked. I can be sympathetic to people who do want to ban him though, as it can be frustrating to basically exclusively play with the new champ, particularly if the potential issues above are common.