Right now, new Warwick is overpowered because of the sheer amount of map information he has from his W. It effectively allows you to scout as you can with Quinn's W or Ashe's E, and it reveals low health enemy junglers. That said, that's largely all he has going for him. He's pretty trash otherwise.
He has insane out of combat movement speed, but that doesn't translate to much. His initiation range is pretty sick, but then again Vi's Q, Flash, R combo gives her better (or at least the same) initiation range as you can expect to ever reasonably get with Warwick's Infinite Duress, and it can't be juked or bodyblocked. His drain-tanking is decent, I suppose, but it's pretty easily beaten by Grievous Wounds, kiting, or burst damage, and it's hard to itemize in such a way that you can make use of it and still deal with all those weaknesses.
He REALLY needs to get a portion of his out of combat move-speed in combat. It's very awkward to be chasing someone and have a stray caster minion reduce you to turtle speed. Q is a pitiful and short ranged gap closer, and asking enemy champions to very politely not kite you certainly doesn't work. If you miss your ultimate, you have absolutely no way to followup. The same is true of Flash. If they Flash after you R, it's almost assured that you won't catch up to them unless you also have Flash available.