Jungle Karthus approves.

I feel like about the time you'd finish building it, you're at the point in the game where jungling speed stops being relevant.

Diana

I just dont unestand how the smite enhancement is at all useful.

Still a terrible item.

Nunu loves it now. If Smite is up more often you can counter jungle faster.

Diana

Jungleraka.

Maybe Riot has some new AP junglers planned?

I'd hope so, since there really aren't many. The last one was Diana, and the only real viable ones are Diana and Fiddlesticks. I supposed it would be good on jungle Nunu, I mean the consume + less cd on smite would be pretty good on him. But I'd assume getting madreds or the other spirit stone items would be better on him.

Try running it on Nunu, you can counter so hard with smite + consume, and having an even SHORTER smite makes you even more obnoxious to deal with.
He also benefits from spell vamp + cdr nicely, so it's a good fit on him. You can get that, then Void staff for some mid - late game damage boosts, then go pure tank/support from there.