I've used a Garmin for years and I'm very happy with it. I have free lifetime map updates and, thanks to a youtube video, I can replace the battery myself, said battery being easily found on eBay.
The feature I find most valuable on a GPS is the ability to add and edit POI (Point of Interest) files. I have a listing for all of the Ford dealers in the country for truck repairs, as well as all of the Walmarts and, more importantly, those Walmarts that don't allow overnight parking. :)
There are websites that freely provide files for every interest imaginable (POI Factory, for example) such as specific restaurant chains, roadside rest areas, dump stations, gas/fuel station chains, etc.
I have seen android apps, Walmart No Parking for example, but they are stand alone lists and are not integrated with the GPS function.