I was only offered a replacement, but they had a few in store (and I also got mine through a carrier, so it was a different situation). Maybe before you go in, just give them a call and ask them to check the stock. That's what I did, and she said to not bother booking an appointment, just come in and explain and they'll see me right away - which was on launch day, so I was grateful for them squeezing me in.
He basically said to me, "It's unlikely because it's day 1, but I have to tell you anyway that it may be made of refurbished parts." I'm like... I don't think after a few hours there'll be any refurbished devices just yet lol.
In Denmark we don't have any Apple stores, so I will have to call their phone support during Monday or Tuesday, at least as soon as possible.
It will need to be shipped back in either way, no matter if they just refund or swap.
I'd much prefer a swap to a new phone, unless stock is low and I have to wait several weeks for a new unit.
Will update when I've spoken to them on the phone.