Play it with my girl friend & on the way to work. Know a fair bit about how it works but my god its ridiculous to get into gyms, similar to the OSRS new skills high score racing. Its stupidly competitive.
I've put a few hours into it and walked around, but there's students in my area which are in the level 20 range with Pokemon at 2000 CP already. I've managed to find a few gyms which somebody has taken out and joined but quickly been knocked out again shortly after. You get bonus exp/coins for holding the gyms which then can be spent on lures to get pokemon easier...which makes it incredibly hard to keep up if you can't get in a gym.
Hatching eggs works incredibly well for getting decent pokemon, got myself a Aerodactyl from one was well happy.

also found out that the starter pokemon are in 2k Eggs so its a way to train those.