I think it's both. The game isn't great on it's own, and I bet the AR will feel tiring after a while like it did with Ingress. But this is amazingly close to the real-world idea of Pokemon so many of us have wanted since childhood.

Last night I went for a walk in the middle of the night to a nearby park. I encountered a few other "pokemon trainers" on the way (it's really obvious when someone is playing), and at the park were at least 30-40 other people, spread out in small groups, some hanging out in spots, some wandering around the grass tracking a Pokemon...

Seeing Pokemon in the real world is neat and all, but meeting lots of other "Pokemon Trainers"?! Wow, that really made me feel like a little kid again. I hope the population stays active until they add battling. It seems like it would be incredibly dull playing this game by yourself without running into others.