I had success the two times I used it. There are a lot of variables at play here: which ship, how full, what time of day, how crowded your location is, the server’s mood, etc.
I would suggest it’s not a good option for people who stress easily. Your order might not come. It might be long in coming. It might be fulfilled incorrectly. The app might show “delivered” for 10 minutes before it actually shows up. I think it works best for those who are able to go with the flow.