IMO it's more viable than AD Kog, especially in ranked play.

It's safer to play, provides more utility earlier (Maxing slow first), doesn't gimp Kog's other abilities, and BAB ends up doing just as much damage as AD Kog + MBR, minus the AS. You just need to be good at leading people with your ult.

All of that aside, picking Kog in general for ranked play is...questionable...

He's fun as hell to play so have fun with him in normal games...

it's like ap ezreal. it's bad, but ppl still insist it's good.

and no, don't build ad kog either... it's called mpen + bloodrazor.

AP Kog'maw is definitely viable. it's mostly ultimate spamming and takes more skill, since you have to predict where the enemy will run, rather than "right click right click right click"

Ult spam ftw

lol yes, I got laughed at for running ap kog in my last game for the first 10 minutes, untill I carried hard. Ap kog is better for laning and team fights imo,He pushes lanes very very well, which is a plus, at least for now.
Plus you get to do a good amount of damage from absolute saftey, and if you do get mobbed, you just ult yourself a bunch and chase down a kill with your icathian surprise.

here is how to build kog...

w/e boots
malady
bloodrazor
frozen mallet
win

it's brainless, and you'll do 5x as much magic dmg as any ap kog.

ya u build full AP, get blue buff and nuke from 2000 miles away. once they get hit by your nuke, rylai's kicks in and they're SOL.