In buying a coffee with BTC my main concern will be to have to pay at least 5 cents for a transaction fee.
By paying with card the merchant pays the fee while paying with BTC we pay the fees. I think that's the main adoption problem in buying a coffee with my bitcoin
I think you'll find merchants would give you discount to pay in bitcoin. Lot of gas stations give cash discounts, the credit card fees are built into the prices, don't think your not paying them.
I would rather give .5 to a miner, give more money to the merchant and keep 3% away from the bank regardless.