I know these pages don't like to hear from people with few posts (this is my first). I have been researching getting an iphone 6s with this deal, and converting to Verizon. I haven't purchased yet but I have contacted both ATT and Verizon, and here is some information they told me.

ATT: If you sign up for no contract and only use the phone for the 15 days and then cancel service, they will reimburse the funds for the time you didn't use. I was also told there was no cancellation or set up fee. I'm skeptical that there is no set up free. We will see.

Verizon: The rep indicated there are no issues with using an ATT iphone 6 on the Verizon network. I have read several times that the ATT phone will only work where there is LTE coverage in the area, but the rep said she had not heard that, and the phone should work just as a Verizon phone would.

Anyway, maybe I can provide additional data points as I go through the process.