For some reason, Kerguelen island and quite a few others in the Indian Ocean don't even exist on Nokia's maps.
Japan/Korea/etc are essentially not covered at all ... they don't even seem to have any roads except for the most major highways—Tokyo on here.com literally has like five roads!—and what very little data they do have is often wrong.
Even Apple does vastly better... oO;
I've used it in South Africa, Mozambique, Botswana and Namibia, and was very impressed. Little tracks that hardly qualify as a road are there, and reliable. The other big deal in that part of the world is that both maps and navigation are 100% functional when offline.