Google Maps can download maps beforehand, but for some reason it won't let you plan a route without an internet connection. Probably because their route-finding algorithm would crush a phone or something :)
In the latest update, 7.0, there's quite a bit of conversation that this is no longer possible. It's recently come out that it can be done with a gimmick, typing 'okay maps' I believe, but it remains unintuitive as a primary task let alone worthwhile feature.
That is definitely a thing that you don't appreciate until you have to use it. We were on road over the long weekend and were lost with no network connection. Thanks to offline maps on my Lumia 920 I was able to find the nearest road offline and get back on road to our destination.
I don't ever post here but figured I'd add my two cents to this.
I got a Nokia Lumia 928 about 40 days ago (just passed time for insurance). This past weekend I went on a trip from Seattle to Yellowstone. We had four people in the car and in most of Idaho and most of Montana there was very sparse 3G or LTE connection. My phone was the only one capable of doing offline GPS navigation.
I've been quite surprised with how much I've enjoyed my Windows 8 phone and only become angry with the lack of games when I'm on the toilet.
I recently returned back to the UK from a 2 week long US road trip, covering 2000 miles. We downloaded the Nokia Drive data for the states we were visiting in advance onto my girlfriend's cheap Lumia 710, as we wouldn't have any data connection (not wanting to incur roaming charges). We were utterly dependent on the Nokia Drive app, and it performed exceptionally. Definitely recommended in place of a dedicated satnav.
