There's a trial near me of ground-based autonomous delivery robots (though it doesn't cover my area) which seems to have been pretty successful. People are using it and it seems to work pretty well from what my friends in the area have said. There have of course been a few hiccups but nothing major (it helps that the delivery robots are cute and will ask for help if they are stuck or need something like a button pushing to use a pedestrian crossing). The main limitation is that their range is only about 2 miles so they basically are only really saving you a quick trip to a nearby shop.