I think it's a bit of familiarity. Remember that a lot of these guys have been at it for over a year on the same maps. They know all the nooks and crannies and know where all the weapons spawn. I am starting to get better now too knowing that I can't just run somewhere blindly. There is almost always a sniper ready to take a rookie out. As far as flying, I am still pretty terrible at it. I practice on the tutorial level a little bit.