The only drawback to VZ Navigator is the small screen. On our way back, there was an accident on 95 and the road was shut down. I was able to successfully map out an alternate route on my GPS, I think that would be rather difficult on a cell phone. This is where most GPSs fall short - when you deviate from the course on purpose all they want to do is get back on the course. Only now are GPS units coming along with the ability to navigate around a traffic jam.
My DH's Acura has the built in NAV that shows accidents ahead and reroutes you automatically. It is great! My Acura has a built in NAV also but doesn't have the traffic alert and reroute feature which would be handy on long trips. I do love our NAV though. We have driven to WDW numerous times so I have the Poly programmed in from past trips. Now when I get homesick for our favorite resort I hit the NAV to the Poly and hear him (the NAV voice) tell me how far I've got to go! Only 944 miles! LOL!