Hah, free Zilean week.
Honestly, fantastic champion. Takes a lot of ramp up time in order to become a sustainable, tanky powerhouse. I don't think he's T1 material but T2 is looking pretty safe.
Kog'maw has been bumped up to T2. The only thing keeping him from being T1 right now is the prevalence of gap closers such as Akali, Jax, Lee Sin, etc., the list continues.
BTW, for all you Zileans out there: Tear of the Goddess is all you need. Really. Early game might suck a tad more, but you'll never want to press B again.