With some (not all) authorized resellers there are additional contracts that can penalize a customer if they change their plan/features or phone during the first 6 months from activation. I don't think Best Buy has such a policy, but keep that in mind. Make sure you ask if there are any additional contracts/restrictions before buying. Good luck.
I have always bought my phones at a Verizon/AT&T store
when i've purchased new phones - is that necessary? What will I miss if I buy at a Target or Costco? I was thinking of buying at another site for convenience - what is the downside?