I just made my first google express order for boots on shoes.com. Got 30% off (promo was on top of shopping page) then there was another 20% stackable promo that popped up by checkout.
Went from $138.56 to $78.79 shipped!
ETA 20% promo on first order is HOLIDAY18, and many times are 30% on top of that. (Hint you can switch google accounts and use 20% promo again!)