Apple began accepting online orders at the start of the week, but Friday was the first day of cash sales of the gadget, which is thinner and longer than its predecessor, the 4S.
But users have been abuzz over content errors in its map application, which replaces the Google maps used by Apple in the past.
Users have been posting pictures on blogs of mislabelled or missing locations, along with other oddities.
One showed the law courts in Vienna labelled as the "Palace of Justice in Nuremberg" - actually some 500 kilometres away in Germany- while another image showed the Eiffel Tower lying flat on its side.
The All Things D blog quoted an Apple spokeswoman defending the service: "We are continuously improving it, and as Maps is a cloud-based solution, the more people use it, the better it will get."//DPA