For our (now retired) driverless car, there were two reasons not to use ROS navigation:

 * Navigation using the DARPA-defined Road Network Definition File (RNDF) had already been implemented for the Urban Challenge competition, before porting to ROS.

 * The standard cmd_vel (geometry_msgs/Twist) interface that works so well for most robots is unnatural for vehicles using Ackermann steering. They prefer something like this:

 http://docs.ros.org/api/ackermann_msgs/html/msg/AckermannDrive.html 

I believe that kind of interface could be added to the ROS navigation stack. If I were still working on that vehicle, I would probably try to do that.