I didn't think this would pose much of a threat at first...
I'm not too sure about the practicality of Hypnosis with Crobat if you could just fit something like Brave Bird and U-Turn on the same set.
Hmm, this is going to be a really big potential headache... I'm just theorymoning here, but... imagine how lethal it will be in conjunction with SpikeStacking... Just by switching in and being neutral to Rock you'd take 68.75% from SR/3 Layers of Spikes/Super Fang. Not even Blissey will be surviving that for long after that. Let's say Crobat has Taunt or something... Stuff like Blissey will assuredly go down or have an easy time dying within the next turn/switch-in or two. Note: Damage from standard SpikeStacking is 37.5% per switch-in.
If you're netural to Rock and this happens... (SpikeStacking (37.5%)) * Super Fang (2) - Leftovers (6.25%) = 62.5% HP damage dealt... (68.75% without Lefties). 62.5% + (another switch-in) 37.5% = 100% or you're left with 1-3 HP... Yeah you're dead... You will not be able to switch-in again until you've waited a couple turns for Leftovers to work its magic, cleared away the Spikes or if you can pull off a recovery move (good luck doing that against Taunting Crobats). Not to mention if there's weather, Toxic Spike hazards, or other statuses thrown about...
Crobat could U-Turn on a Spinner if it came in, which would probably be a definate kill on Starmie (which is like the best Spinner in OU) if it came in on a Super Fang. CBTar would likely die from a U-Turn as well before it could pull off a Pursuit or it would be very easy to pick off afterwards...
I am just glad none of the current OU got this move (maybe Game Freak finally looked at our tier lists and such).
Then again priority may give some Super Fang users a hard time (Scizor, Lucario, Metagross, Dragonite), but we'll see when we get this to play with in Shoddy.
If Super Fang has the least impact on the metagame I'm guessing we'll see it every now and then, but nothing too worrisome...
If it has a great impact on the metagame I'm nominating Stealth Rock for a Suspect again :P