So far, there's really only one thing which bothers me about the game, but it bothers me enough that I nearly regret buying the game at times.
I really hate the aiming system used in GTA V. On top of the AI making weird choices concerning who it chooses to lock onto (a guy is standing right beside me, but I start shooting at someone across the street..?), I've found that having a white aiming reticule is also a problem. There are a lot of times when it blends into the background, and I can't see it.