For me the game runs fine i have a iPhone 6s Plus and Ive never experienced errors or the game crashing. Most people that experience these things have older phones (iPhone 6 or 5) and people with androids. The gym raids and battles can sometimes be a little slow to react but thats about the only problem that I experience when I play this game. I like the new system with the longer the Pokémon is in the gym the more coins it will earn but I feel there should not be a limit cap on how much coins it can earn. The new gyms make battling more enjoyable and less frustrating. The poke stop added to the gym is good for small rewards. The game is fine but can obviously be improved and hopefully it does.
_schwim_ about Pokémon GO, v1.37.2