ATTingular in my opinion will be the place to go - for one reason. they are familiar with activation/plans etc.. AND I am eligible for a 15% discount on my service since I am a teacher in Mass.
For that alone, I am not going to an Apple Store. I have a sneaking suspicion that purchasing and activating are going to be a really time consuming effort there. Not to mention that they will most likely give me a blank stare when I present my Sprint bill for number transfer, and my union card for the discount.
After all, this is the first time they have sold a product that will require "activation" of some kind.
My guess is ATTingular folks will handle it just like any other phone. Choose the phone - choose a plan - hand over your cash - leave store with BIG grin!
(of course the last line applies to iPhone - not your regular average Joe phone)
Oh and as a bonus - the store I'm goiing to opens at9AM - a full hour earlier than any Apple store in the mall!!
Kurt