(a) as long as you get in, do your business, and get out of the way, nobody cares. Relax.
On the other hand (you knew there was an other hand, I'm sure) EVERYBODY hates the a*******e who camps on top of a pump fills up, goes inside, gets a hot dog, pays for it, eats it, pays for the fuel, chats up the clerk, mosey's out to the rig, then sits in it for a spell calculating fuel mileage and where he's gonna spend his NEXT vacation before finally pulling out of the way.
Those guys deserve a full set of flats all 'round. Plus a dead cell phone battery.