When I am the one standing there, studying, I try to be aware of people coming up so that I can get out of their way.
The only time I am irked by people in my way is if they are not shopping, but instead carrying on an unrelated conversation, totally unaware that they are not sitting at a table in a café, but blocking shoppers from getting things done.
There was one time when a woman was taking forever trying to figure out which item was the one she wanted. Finally, I reached around her and got my item. "Well!" she exclaimed.
I looked her in the eye and said, "Ma'am, I said 'Excuse me' three times." I saw her realize it at that moment that it was not some disembodied voice saying Excuse me, but that it had been directed at her. She grabbed up an item, said sorry, and left.