Three things they notice
Whether the delivery arrived in the window, whether the person at the door was professional, and whether the order was right. Almost everything else is secondary.
Communication carries the experience
A customer who knows a delivery is running late is a customer with a normal experience. A customer left guessing writes a review.
The delivery represents your store
Whoever knocks on the door is, in that moment, the retailer. That is why professionalism at the door matters as much as speed.