I was mightily impressed seeing ADS/B in action in Alaska. All participating traffic's position, track and altitude overlayed on the terrain picture in the cockpit. The difference in confidence level from this and dodgy radar based information from ATC due to terrain masking made the point in some distinctly poor vis and low cloud.
However one has to admit that the FAA were funding all the ground stations and provided the first 100 odd aircraft fits FOR FREE so that a realistic trial could be made.