He said the range is 10 miles, which is good enough for most residential areas. They are aiming for delivery in 30 minutes. The drones are autonomous: you plug in the GPS coordinates and away they go.
The biggest challenge (again, according to Bezos) is the redundancy, "making sure it doesn't land on people's heads."
My question is: why announce this now, 2 to 3 (or more) years out? Are they gearing up to get governmental regulations?