Does the coffee shop/ restaurant/ bakery/ gift shop etc charge a premium to accept bitcoin when you walk in and buy from them using bitcoin compared to the local fiat price?
If so.. how much in your experience/area?
There is no reason for a shop to charge a premium.
However you do have to figure in the buy sell spread. The shop is obviously going to use a btc to fiat conversation rate based on the sell value as that is the value they will get. You however paid the buy rate. Assuming you used the same exchange (buy sell prices vary widely on different exchanges) and the btc price didn't change you would in fact pay a premium.
Luckily the buy sell spread has tightened up over the last six months.