I have a hard time seeing my father or mother ever using digital currency. I don't see the mass public ever adapting to online currency. There is a considerable step in technological knowledge to get started and another leap forward in knowing how to protect your wallet. It's not as simple as keeping it on an exchange anymore.
Using it in lieu of credit cards, seems overwhelming. I can't make a simple purchase and go without the desired number of confirmations which could take 10 minutes to hours. I do not see patrons waiting nor retailers waiting for the confirmations. Lower fees do not make up for this.
now imagine your grandmother ready to buy the hand bag you tell her
"granny sit down dont worry about your purse or your reading glasses here take my phone and press the screen 2 times in the middle" once to open the wallet another to scan qr code. then you say "press the send button"
and as for the waiting time. as soon as she presses the send payment. she can go on to make cookies or do some cross-stitching and in 10 minutes she will get a confirmation email (no difference to fiat merchants) and the handbag will be on her doorstep in 3-5 days (no difference to fiat merchants)
once the payment send button is pressed the customer can walk away and do other activities whilst waiting for their goods to be delivered.
i only see a problem with instant access online content. .. but wait most people prebuy their balance (depositing early) like buying microsoft points or steam credit and then eat into that balance as and when they like. so thats not an issue also.
soon starbucks will probably have a prepay system .. oh wait they do..
all that is left is for starbucks to allow you to buy prepaid cards with bitcoin...