We have found that the nav system is definitely not a replacement for a good gps unit. The problem with the Qualcom gps is that all the routing info is not stored in the unit itself.
If for whatever reason you are not able to take a road or street (road closed,accident,or whatever) and you ask the unit to recalculate a new route,it is not very quick at doing that and that is a real problem when you are moving.
What causes the delay is that it has to keep sending and receiving the info by sattelite,which can take time and can put you in a bad situation.
Our Garmin gps can recalculate in just a few seconds,while the Qualcomm unit can take up to several minutes and that is just not acceptable in the real world.