Sorry I'm a newbie here, maybe this has been discussed before.
After reading several posts here it seems there is a conflict between the need for high speed of transactions/verification and security.
I think security is the most important factor in order to make sure the big bucks in the system are safe and resistant to various attacks.
However there is a strong need to pay at the 7/11 etc without waiting a long time, and also the use of "light clients".
In Hong Kong they have this amazing thing called an octopus card. You load it with money, and just drag it past an rfid reader when you pay. Very fast and easy to use, no code to enter etc. It was originally made to pay for public transport but gradually more and more stores started to accept this payment method. Sure if it gets lost or stolen your money is gone. But you don't put thousands of dollars on there at once anyway. Then it's up to each user to balance risk vs convenience (money lost vs frequency of reloading)
Waiting 10 minutes (or more?) is not a problem for Transaction between banks, buying a house or a car.
The foundation must be solid.
The "quick cash" bitcoin would be like the octopus card, giving users the convenience while limiting potential damage.