U-turn I guess is okay as a filler option on Choice Specs, but otherwise the ability to pivot really isn't all that notable for offensive variants of Articuno. Particularly since it could easily not be worth taking Life Orb recoil and/or Stealth Rocks, and the paltry damage it deals is not likely to be significant or help put its checks into KO range. And since we're not trying to Slow-Pivot here, it would make more sense to run something like Calm Mind or four attacks in the last slot to minimize the need to switch to begin with. Switching out yourself when you predict a switch accomplishes the same thing as pivoting with U-turn. So all-in-all, U-turn is not that great here.