I pre-board for the overhead space. I was in 1F last week and the first 1K to board and there was no overhead space until row 3. I think if UA did a better job of ensuring the overhead space was used by the people in those rows - think LH, there would be less angst for pre-boarding.

If not in row 1 I am in row 7 and the number of pax boarding early who put their carryon above rows 7-9 and them continue walking further back to whereever their seats are astounds me. It is not my role to police this and apparently it is no one's role.

This is why frequent travelers want to pre-board so their carry on goes above them on the plane and they can keep an eye on their belongings. The few times i do not have a carryon I am one of the last to board.