Personally, I've generally found Google Maps to be pretty good - I travel to two or three cities a month for various things, and it's proven very useful for both getting me to the city and then navigating around via public transport.
Except in Sofia, where public transport timetables don't seem to have been added to Google Maps. Still, I got a lot of walking done that weekend ;)
One thing that's definitely improved over the last few years is the traffic-jam alerting; these days, I suspect it's more timely than the Highways Agency's system, and a big red mark on your route is a lot more useful than the standard "A1234 closed at junction 22b" roadside warnings which generally mean absolutely nothing to anyone who hasn't taken the time to memorise the whole of the UK's transport grid.
Though admittedly, the first thing I do when configuring a new phone is to turn the vocal guidance off!