I've had a PN-20 for more than 3 years and have found it to be difficult to use. It is non-intuitive and if not in constant use very difficult to go beyond simple tracking. I haven't used it for a year and all the city detail is missing. I reset the unit to factory settings; lost all my difficult to enter data, and had the detail until I tried to shift to another city and all the detail disappeared. Nothing below 8 mile resolution. Over the years I've gone to Mac computers and now can't reload my SW and I'm stuck with an expensive yellow brick.