Does it have to drop packages from 3 meters off the ground? I'd rather it landed and gently deposit them. Even so, this won't suit all users - what if you're not in, or in an apartment? Guess it works for people with fenced back gardens. Still, its the future of delivery. These things can get work arounds.
It is the future, but not the way everyone thinks. Everyone thinks drones will be for the last mile, but the reality is they'll be for the last five metres. Amazon will have a vehicle that can drive down your road and the drone will take your package, fly out and return to the van. Each van will have a minimum of six drones and the only time the driver has to stop is when all drones are out of the vehicle. I imagine that consumers will be able to set preferences, like leave at this particular spot or only attendance required, for which it would ring the bell/phone/app of the person.
Once they sort out autonomous driving, then humans will vanish from the delivery process all together.