I'm very much looking forward to using Nattorei. It has some of the best mixed defense stats in the game combined with a solid attack stat and an absolutely LETHAL Gyro Ball. I believe it's the only Steel type (outside of Dialga) to resist both Water and Electric attacks. It's a shame it doesn't learn Rapid Spin or Earthquake, but perhaps it will find a different niche. Leech Seed on a Steel type with those defensive stats is nothing to sneeze at. Explosion is always welcome. He has a really solid Power Whip.
Any word on its ability? It's hard to judge him without knowing what it does.