Been trying her. It's quite a bit of fun, but can't imagine taking her out for a spin when I could just grab Trundle, Shyvana or Nocturne.
It's nice to have the option for another AP jungler though. Can probably be pretty decent in specific team comps. I would hope for a few buffs/fixes before I can see her being completely viable.
---------- Post added 2012-08-10 at 11:30 AM ----------
Addendum: How do you build her btw?
So far, this is what I've been thinking about:
AP (flat) Blue + Quints
Start boots + pots
Pick up Philostone + Kage's asap, possibly add a Doran's Ring if I can afford one at an opportune time.
First major item Rylai's.
Upgrade to MPen boots
!! Add Abyssal Sceptre + Add Haunting Guise !!
I am still in doubt about the remainder of the game. I can see Zhonya's being nice on her. Lichbane is great. Nashor's gives CDR and some mana regen + AP, which are great stats for her. Just the AP is slightly lower than it could be on other choices.
Let me explain my reasoning for the MPen + Sceptre + Guise combo:
1) You're melee range
2) You're squishy
Combined, the three items essentially let you deal true damage to the majority of the champions (by removing 60 MR from them) by that time. Guise also gives you a bit of bulk.
If you have the money to spend, later game you can drop it for a Voidstaff and/or Deathcap.