Google Maps for Android provides area-based offline maps, with a time limit that is not enforced.
It's been very useful to me personally, not sure what's unusable about it. I find the online version less usable because it nags me about GPS and obstinately only stores search history online, coupling it to the global Google Activity History setting.
If you have a GIS system, that is able to use Google Maps as the basemap, you still don't have the ability to save it for offline use. The APIs/libraries/license agreement with Google that these GIS systems use won't allow that.
Not that other providers (Bing, Here, etc) are any better. Your only way is to download OSM data/obtain local ortophoto and make your own tiles.
Is navigation working off-line now? Last time I checked, it didn't. And Google Maps, even on-line, are quite bad at being a map, with the completely unreliable way of rendering street labels. I've used Google Maps off-line in a pinch a few times, but it wasn't too pleasant of an experience.
(Call me entitled, but I don't think it's too much to ask of an off-line map to offer point-by-point navigation and searching through the DB of addresses and POIs in the off-line map. When you can't do it, I get the feeling someone doesn't want you to use off-line mode, and is purposefully overcomplicating things.)
All those things (except display of some street names) work for me offline on my Android phone, but only for driving directions. You have to save an offline map manually first, somewhere in the settings or sidebar.
