I tried using it in Bosnia, once, and it decided to use an abandoned airfield landing strip as a shortcut. Wild stuff.
I frequently drive through Serbia/Bulgaria/Montenegro/Macedonia, and if you ever do, do yourself a favor and install something OpenStreetMap-based.
Otherwise, you will be missing new motorways, get thrown on unpaved roads, or even asked to drive on roads that just do not exist anymore.
to be frank, I have a feeling that Google has more / better data.
I haven’t come across anyone using Apple Maps while living in Japan, most seem to use Yahoo! Maps or Google Maps.
Noone in my circle with iphone uses it. Most of people are using Yahoo maps, which is way better than google and apple maps combined.
And they are planning to make it even worse with ads, so.