INGRESS, the 1st game from niantics, is a very largely popular game on android, i have played it quite a bit and its fun, but better played with friends so we capture the portals.
with pokemon go, considering the idea is about the same, i can only expect a fun game also, but as yuuhi said, wont be as impressive as they are showing it in the videos (ingress teaser video is way more than the actual game also).
Only bad thing that i have read about pokemon go so far, is that pokemons will be scattered all over the world, and they will do theyr best to put a pokemon near its "natural" habitat, so a fire pokemon most likely will be near a volcano for example, wich means that if your country doesnt have a volcano, you have to travel to get it.
however, if the fights they plan allows us to conquer the defeated pokemons, then i see a great way to find other players in real world and complete our collection.
btw, if you want to join in ingress, i have LOTS of recruitment invites, altho you can create a free account without invites