By "last minute," what exactly do you mean? There have been several times in the past couple years where I've been watching the SP for the last half hour of the day, indecisive, and then with literally 2 seconds left in the trading day, hit "enter" on an order to buy. the median execution time on orders on the ScotiaItrade.com site today said 0.5 seconds from the time the order was entered.

It could be that these last minute orders are sometimes just last-minute orders from small retail schmucks like myself, who are hesitant but want to get an order in before closing.