I've recently changed my phone to a Blackberry Z10, mainly because I liked my Playbook so much and the OS is a more refined version, and that it has batteries you can swap (rather than sealed like many) which means you can carry a spare with you and it has a microSD slot so will take up to 64GB cards, add in the onboard 16GB and it provides a great storage capacity.
http://en.wikipedia.org/wiki/BlackBerry_Z10
It like many phones, had a "download on the fly" model sat nav app. These in my opinion are useless as if you lose your phone signal you lost navigation, and often poor signal is in remote areas where you may just need the mapping.
My previous Nokias had the excellent Nokia Maps, this downloads whatever countries you choose to the phone meaning the maps are stored locally so don't rely on mobile signal to access them, add in that if you happened to roaming in another country data access would be hideously expensive too so having mapping data downloaded on the phone in full previously at home is again a plus.
The system on the Blackberry Z10 was quickly dismissed as a toy sat nav app, then I found the excellent "Don't Panic" app by Mireo.
http://www.mireo.hr/en/
It's available for the Blackberrys, iPhones and Android phones and was stunningly cheap. All of Western Europe (2.2GB of data) downloaded via my home wifi to the phones SD card for about £12!!!
I use a BMW Navigator III (rebadged Garmen Streetpilot 2820 I think) on my KGT, and have a couple of TomTom devices at home but find "Don't Panic" slicker than all of them and MUCH cheaper. Seems to include some 3D buildings on the route and speedcamera warnings too.
Add in that modern smartphones have MP3 players for those tedious motorway slogs and good cameras in them too nowadays, my previous Nokia N8 had a 12 megapixel camera, the current Z10 has only an 8 MP one but produces some awesome vibrant HDR pictures via software trickery that actually takes three images when you snap away then takes the best "parts" of each and melds them into one. Or something .... either way they're awesome quality....
My Z10 was free on O2 with unlimited phones calls (landline and mobiles), unlimted texts and 1GB of data for £37 pcm. As I'm usually in the office or at home I connect using the relevant wifi's so rarely eat into my 1GB data. To be honest if I had better signal at home I'd cease my landline.
I got a bag from Hein Gericke for a couple quid, connected it to a RAM ball system
Since then Ive refined it by adding a "powerbank" USB battery top up like this
http://www.ebay.co.uk/itm/Universal-6000-Mah-Micro-USB-External-Battery-High-Power-Bank-Charger-Grey-/230927673532?pt=UK_MobilePhones_MobilePhoneAccessories_MobilePhoneChargers&hash=item35c45ca8bc
into the bag to make sure the phone stays charged ... after it ran out "JUST" when I needed it in Minehead