Confirmation in transaction is not a problem anymore, just take a look at how we bought digital goods. As soon as we send the amount to the address provided by the site, it immediately mark our transaction paid after a few seconds. If that's what the stores in real life will use, then transaction confirmation won't be a problem.
But if we will use the traditional confirmation waiting, then that will really slow down the transactions in the stores or if you want it fast then you pay high transaction fee.