I don't find the game all that fun to be honest. Mechanic-wise it's much more shallow than the traditional games, just a matter of walk, catch, transfer for candies, use candies to power up and evolve, battle people. If they tied similar GPS functionality into the existing Pokemon games framework, the game itself would feel like it had more depth.
As it stands, the game is more an exercise supplement, than a game you play while exercising. I exercise at the moment but the game itself doesn't interest me enough to pay attention to it while I run. It's more distracting than anything.