Never thought I'd want a GPS as I am good with maps. When I was a draftsman with the NCDOT in the 70s, I used to draw road maps.
But several years back we acquired a TomTom XL340. To paraphrase the old credit card commercials, I never leave the home county without it. I added a handlebar mount for it on the bike, too. Much easier than taping an open map on the gas tank.
Two must-have features for me are the lifetime map updates and real-time traffic info. We've had it warn us of major traffic delays ahead and ask if we want to be re-routed along a faster route. A very nice feature.
The library of Points of Interest includes many features an RVer might want: gas stations, grocery stores, parking lots, etc. For example I can tell it to head for the nearest Walmart ahead that is along our current route.
When the current GPS bites the dust, it will be replaced immediately.