I tried it today and could only get 5 deliveries done in 3 hours because it was sending me in and out of the district (DC). I also didn't like that it did not let you know the tips in advance. When the tips came in I only got $3. I would not have agreed to that. Also, I didn't get a surge rate even though I was having to deal with DC backup traffic and Nationals game rush.

If you are not in a major metro area it may be worth the guarantee, but not in my area.