How do BTC payments work at real-world shops? At CoinMap, I can find several coffee- and other brick-and-mortar shops that apparently accept bitcoin payments. How do these transactions work? Do I have to stand at the counter for 10 minutes and wait until transaction gets confirmed, do they use some kind of trick to make the transaction time bearable?
Depends on their infrastructure. If they use an intermediary (like bitpay or something) it will be instantaneus, since bitpay is the one that takes the risk for double spends and accepts payment fast.
In case they have their own infrastructure, it may depend on what they do, if they accept one confirmation for the payment it may not take much otherwise it may take longer. I don't think any of those shops do that by themselfs, most probably the will have an "acquirer" for bitcoins.