Executive parking spot?
I rarely ever back in. Now at work I pull through since I arrive early enough, and at my apartments there's no way I can back my car into the spot without taking some other vehicle out--the spots too small and I don't have the room to manoeuver. Other than that it usually doesn't bug me when people back in--except in one special case.
The only time I got really irked with people backing in was a special group of cretins which I ran into when I lived in the Seattle area. I took the train to work every day, and there's aways the balance of trying to arrive early enough but not waste too much of your life standing around for the train when your BCC (Blood Caffeine Content) is dangerously low. Anyhow, the cretins in question are those people with inferiority complexes who owened SUV's without any legitimate need for one--the people that are compensating for something who don't have the requisite vision, motor skills, reflexes, or IQ to drive a large vehicle. They would always try to back in, poorly and needing multiple attemps, and effectively block off the parking garage and in a couple of cases would make people have to sprint to catch the train. My logic was that you need to be on time for work, but your source of income won't be compromised if you're late coming home, so I'd pull head-in and then just wait for a good break to back out when going home.
So, my thoughts are this--if you want to back in, fine, but if you need multiple corrections to fit into the spot while attempting to back in, you need to learn to drive your vehicle.