He's pretty awful right now, he takes so long to scale and the games are usually over as soon as he starts to turn on. It also doesn't help that he has to stand still to utilize part of his kit.
It's kind of like being on a jeep mounted .50 cal machine gun in the fog and only able to see 20 feet in front of you. The shit you see gets obliterated, but all the stuff you don't jumps right on you and rips you apart.
It basically requires a Juggermaw comp, and while a lot of those champs are meta, who wants to put all their eggs in the kog'maw basket if the basket is still only a pile twigs until 20 minutes in.