I have just seen that Amazon are going to test drone delivery in one undisclosed area of the UK. The report interviewed someone in America who has drone deliveries. When asked about the noise he said it didn't bother him.
The noise was my first concern as it sounded quite loud. If they choose to deliver in remote areas that could disturb the peace in a place people choose to walk because it is peaceful. I did see post was being delivered in this way in remote parts of Scotland, but from memory they did not sound as loud.