Decent in constructed(It will at least be run as a one off in tempo mage and other midrange decks imo), busted in arena. To the people saying it won't see play, keep in mind boom is going away, and the only remaining late game minion available to tempo mage is tony, which might not be enough.
And why the hell does blizzard keep pushing tempo mage into being the most RNG based deck in the game?
A really good arena card - especially due to the fact that it is common. Just so much tempo. I'm not too secure about constructed... has kind of the same effect as shredder, but for 6 mana it competes with a lot of great alternatives like sylvanas and emperor. I don't think mages will choose this over the other 6-drops in most decks. Perhaps it would have been better for another class in constructed...
I've seen people asking for nerfs on ANYTHING. If Blizzard one day decides to actually pay attention to the community and starts nerfing as requested, we are going to have a game with only wisps. And still someone would say wisp is op. I'm not even kidding.