I know Rogers gets plenty of complaints (many of them valid), but everytime I've gone to them with an issue they have been great at resolving my concerns. I've been on Rogers for about 15 years or so, but I'm not sure if that really makes a difference.
Back on topic for WP, I used my Lumia 900 to navigate this weekend and it worked great. Using Nokia Drive, I downloaded the Ontario maps (about 95MB) over WiFi before I used it and then was able to navigate even when I lost my data connection. It took me different directions going to/from which might have been due to traffic (I would have chosen the same way knowing the traffic patterns) or it might have been a fluke. Regardless, I used the app to navigate for about two hours and it only used 20% of my battery, which is much better than I thought it would. The only problem is I had to keep the Lumia in my cup holder which means I had to look away from the road to see it, but if I could get a mount for my air vents I think it would work very well.