I recently picked up a cheap refurbished factory unlocked Nokia Lumia as a secondary phone, specifically for the free Offline Nokia Here Drive+Maps support. Considering the expense of getting a TomTom, Garmin, or iGO dedicated GPS unit with world map coverage plus unlimited updates, the Nokia Lumia was a much cheaper option. Having factory unlock, also allows me to purchase inexpensive micro-SIM GSM cards when travelling to avoid costly roaming charges.
In fact, in my most recent trip to Europe, I used it specifically for drive navigation with a cheap removable phone bracket, and it worked just as good as dedicated GPS. Saving me much more than the cost of this phone compared to renting GPS navigation for 2 weeks from the car rental company.
Furthermore, my Nokia phone is lighter, slimmer, and has better (> 720p) display than dedicated GPS. Furthermore, Nokia Here Maps, it also works great when walking around the city, looking for hotel and other POI.
My only complaint is that despite having offline maps for just about every significant country, South Korea and Japan are suspiciously missing, even though I really need them. :(
My biggest compliant with Windows Phone 8.1, running on my Nokia Lumia, is the lack of local offline backups (since I don't trust the cloud with my data), and device client certificate management needed for S/MIME, Wireless WPA-Enterprise, web client certificates, etc. Both of these are features are fully supported for years on iOS and Android, but Windows Phone 8.1 requires sending up MDM (Mobile Device Management Server) on WIndows 8.* to manage PKI externally, as oppose to on the device locally like iOS and Android do.
For my next primary phone, I have want a phablet, and have been on the fence between upcoming iPhone 6 (with large 5.5" of higher display) or Samsung Galaxy Note 4, both hopefully available by the end of this year.
Havinvg Nokia Here Drive+Maps with free downloadable offline maps on the upcoming Samsung Galaxy Note 4 would be enough to tip the scales away from iPhone 6.