GPS mapping is a tremendously liberating technology, because it completely takes away the worry of getting lost. You can simply ride off in any direction and follow wherever your curiosity leads, safe in the knowledge that your GPS will get you home in time for tea.
I have always had a penchant for ad-hoc touring, never pre-planning routes, rarely carrying a map more detailed than a 1:200,000 motoring atlas and often travelling with no map at all. Using a GPSr hasn't changed these habits significantly, but it has taken away the more miserable parts of such touring - being hopelessly lost in monotonous terrain, desperately searching for a hot meal or a bed or just somewhere to fill my bidons.
For me, a GPSr is a piece of self-rescue equipment, like a spare tube or a toolkit. It's not something I expect to use on every ride, but I feel naked riding any real distance without it.