I am having these exact same issues. This is a cell phone tower that is right outside the building where I work. I should have full bars and uninterrupted service in this situation, but experience buffering and lagging load-up of app pages. Not only that, but coworkers of mine who have different phones (Motorola) on the same network have almost full signal INSIDE the building. Obviously, this is a device problem.
I have never used iPhone and I must say that this has left the worst impression of Apple products upon me. I simply don't understand why people have always tried to convince me of how great they are, because between my device experience, and the iOS experience, I hate iPhone.