I do really slight incline. Like either lowest setting on an adjustable bench, but more often just a 45 bumper stuck under the head. That's my primary angle for benching, I rarely do flat. Low decline neutral-to-primates are also really good. There are EMG studies showing low incline to be the best angle (by a considerable amount) for chest development and flat bench is usually somewhere around 5th or 6th.
Moral - Flatt bb is pretty shit for chest development.