A little surprised that I have yet to find any mention of Araquanid or Golisopod in this thread; both resist Pherosoma's STAB as well as Ice Beam, and are quite bulky to boot. Even Araquanid can take her down no problem with a Water Bubble Liquidize.
What concerns me the most about Pheromosa is that she obliterates hyper offense. Think about what Mega-Lopunny does to it with nearly the same physical attack alone and less speed. Having the ability to go mixed with Ice Beam (pretty solid coverage, all things considering) mean that Pheromosa outspeeds literally any unboosted 'mon HO wants to use (even by 1 speed point!). Sure, she falls to a light breeze, but with Psychic Field up, taking her down with priority might be a pain. The fact that an entire team archetype has to play around her and any team support can't be healthy.
It will be really interesting to see what other answers people will have to this monster in the early metagame, especially if we give Aegislash another chance.
This is all presuming OU Smogon standard, of course. I agree that this thing will be a monster in Battle Spot singles, but with Aegislash and less room for it to U-Turn to, I can actually see it being more manageable. That, and pretty much anything that survives it (FOCUS SASH) can probably OHKO it afterwards.