I have Navigon*, CoPilot and several OSM apps on my Android devices, and Google Maps offline mode knocks them all into a cocked hat, for speed of search, quality of results, slickness of renderer etc.. I did enjoy Nokia maps back in the stone age when Nokia wasn't an eccentric choice for people with an allergy to good devices, but don't really fancy a Lumia just to have their kickass maps.
(Also, Sygic for Android seems really nice, from taking the demo for a quick spin, and their support people are super friendly and helpful, the devs actually respond, too.. gasp.. worth a look)
* DO NOT BUY NAVIGON, if you change phone, they expect you to pony up again, and don't let you transfer license. Fuck these guys, avoid them, and avoid their parent company Garmin, too. Too many hours of my life wasted on the phone to the "support" line to rude people with thick Russian accents; I am a bit cross about this :)