I moved to a BlackBerry recently because a. I'd wanted to try one for a long time and b. I wanted to trial some of the BB GPS Solutions.
TeleNav isn't an option to me here in the UK, BB Maps is OK for basic 'Where Am I' Stuff, GoogleMaps is great for navigation a strange city on foot, finding addresses etc but so far the best GPS Navigation solution I've used is
Wayfinder. This is an OTA solution which downloads maps on the fly but it will cache a route to keep data costs down (not an issue on unlimited tariff's).