GameStop is sold out, Amazon is sold out, and none of the Best Buy's, Wal-Marts, or Targets near me have it in stock either. The game is selling for $50+ on eBay. For a $40 game this is a very good indication that it is hard to find.
My local GameStop even told me they didn't get enough copies in to satisfy pre-orders.
Do you think Nintendo just under estimated demand, but if they don't make enough to satisfy pre-orders something else must be afoot. Maybe is was some manufacturing snafu. Or a distribution issue with their shipping provider. Or maybe Nintendo decided to see how many people would download the game from the eShop if it was hard to find a physical copy.
Whatever the reason, I am still waiting to find a physical copy of the game so I can start enjoying Fire Emblem. Have you had a hard time find the game or did you download it?