Delivery.com hands-down has the best promotions (money off, points) of any online food delivery site, but the UI of the site is terrible. Why, for example, do I need to see what restaurants are closed? Why isn't there at least an option to filter those out?
A few restaurants, I know the delivery hours are incorrect. Hard Grove in Jersey City lists a brunch menu on delivery.com that's only available until 1pm but delivery.com says they don't start delivering until 3pm!
Also, delivery offers no time estimates. More often than not, I'll go to Seamless and check delivery times before ordering on Delivery.com.
Great site to save money, less great for a smooth experience.