Re: GPS Dependability....
My Garmin Etrex Vista failed on me. I was drifting down a river I know very well, so it wasn't a big deal. In this case, it was a known problem (I later learned), where the connection to the LCD screen was loose. Technically, the unit still "worked", but the screen had failed so I couldn't see the output.
Garmin "repaired" my unit for $75 (just sent me a new one). The new unit will occasionally produce lines across the screen.
If you like your hunting rifle, you can keep your hunting rifle.