Very interesting. Assuming that the drivers doing a "Rush" order can gather delivery items from multiple businesses in one geographical area, it could mean greater delivery efficiency (and shorter delivery times) overall. Example: orders come in to 4 businesses within within a few blocks of each other. Businesses send their Rush request in to Uber. Uber Rush driver indicates that they are in that area and picks up all items, then delivers them to target area(s).
Another thing this implies is that that these businesses could switch from a staffed delivery service to a completely on-demand one. One of the things the businesses and their customers could see an improvement with is the case where all their delivery people are out making deliveries, and new orders come in. With this, they just make a new Rush request and get a new delivery person.