Plenty of advantages, from what I can see. In addition to what Richland Rick says, my GPS and some free mapping software allows me to plan a cross country route using routes that aren't normally even visible on a road atlas, unless you plan on carrying a detailed individual state atlas for every state you're going to be passing through. Last year I found a lot of excellent dirt and gravel county and township roads to ride on during a cross country trip to Iowa that would never have been visible on my backup road atlas. More than once I've been grateful for the "nearest gas station" feature on my GPS (especially out in places like rural New Mexico), when the needle was hitting "E" and I had to choose between one direction or another in a last ditch effort to find gas.
Another advantage: No written directions, or cue sheets, or keeping track of the odometer. I program in a route, and just follow the big purple line on the screen. If I miss a turn, the GPS routes me back to where I need to be. No pulling to the side of the road to wrestle with a map or an atlas on a windy day, trying to figure out where you went wrong.
I still have all those map reading skills because I started riding long before GPS, but frankly, the GPS system is better. I still carry an atlas out of force of habit, but I haven't had to crack it open in years.
"No matter where you go, there you are."