We have had a couple of different GPS Units over the last ten or so Years!
I find them useful when navigating through the larger Cities with multiple Freeways! Other than that a good Map studied before each Days trip is of much more use to Me!
I will say that they are a great tool, when searching for the nearest Walmart or a specific shopping center! They also help when planning Fuel Stops in unknown territory.
The First unit was a multipurpose unit that was not specific to any Vehicle. The Second one is RV Specific and as such often sends Us in round about the block routes rather than directly yo Our destination!