I think it's really fun! I can't really think of any negatives, other than people being horribly distracted, and those first rounds of outrageous data bills... ;) xx
I think its great because it encourages getting out and walking and exploration. I know many families that actually do it with their young kids. A good family time.
From what I understand it was designed to get kids off their computers/ game centers hooked up to TV and get them outside for some exercise. I keep reading about deadly accidents people have while playing this game and walking out into traffic, falling off cliffs, crashing their cars etc. It is stupid to be driving and playing a game like this. Too many car accidents happen already due to texting while driving.
I agree with the other comments. In Sweden where i am people has been droved over by cars. So i think it is good if you doing it right. I dont like to play any games.