I have no need for the gateway at this time. But you can hit your menu twice then down to Satellites and there is a number that indicates your accuracy. I've noticed that if I'm connected to WAAS it will be in the 10 feet range or less, if not then more like 20 to 30 feet. As far as returning to a brush pile I can get dead on it most of the time as long as I zoom in while going to it. (zoom to 100 to 200 feet/length)
I also think if the same unit that makes the waypoint goes back to it your accuracy increases. (repeatability)