I have used Sygic several times- I have a work cell phone, and a 3$ per month throwaway for travel.

3$ phone has no data, so II need offline GPS.

The hard part was pre-downloading the maps for areas that I needed, but once that was done, it worked very well.

USed no data at all....

Did Minneapolis, Denver, Washington DC that way. All maps were accurate- just no traffic reports (duh)