I've used it a bunch of times, and I think it's the greatest thing since sliced bread. Although I can't specifically address the coupon question, I suggest you try it once (get the $10 off!). When you call the number, you'll talk to a real, live person--you can ask them about the coupons. That person works only in the pick-up department.
We haven't had many issues with substitutions, except right after the hurricane a few weeks ago. It may vary by location. The few substitutions we've had were in our favor--I buy a lot of Great Value products, so they substituted brand-name. If you don't want substitutions, you can check a box when you're checking out.
Although they emphasize groceries, you can pretty much order anything
Walmart sells. While I wouldn't recommend ordering tires through this service, I have ordered cleaning supplies, vitamins, shampoo, hairnets (DD does dance)--never a problem.
You do have to order in advance--this is NOT a replacement for a "milk and bread run". What I do is, I set up an order for a certain day/time that works for me. Then, you can go in and edit the order, up until 1am on pick-up day. So, if you want to stop every Tuesday after work, set it up, then type in your grocery list. Add to it, up until Monday night, and you're set.
There are definitely bugs to be worked out. They had some issues with the hurricane--for example, they closed down the service for a week--understandable, since NC was having serious distribution issues due to flooding. But, you didn't see this on the website until you went to choose your pick-up day/time. They've since changed this--you now see it on the home page--after I complained (yeah, it was totally me!). You're supposed to call 10-15 minutes before arrival--I had an issue where it sent me straight to voicemail, and when they checked their phone, there was no record of my calls. Twice, I got someone else's bag of food (in addition to my own).
All that said, I still love the service. You get Walmart prices without having to actually set foot in Walmart. You don't even have to get out of your car! The employees are helpful and friendly. I don't order much meat from there, but the produce has been fresh, milk has been fine, they even check the eggs before they hand them to you (they give you the choice of having the eggs packed in back or handed to you). This doesn't replace 100% of my grocery shopping, but it cuts down on my time spent schlepping through stores. And if you were a better planner than I am, you could get a lot closer to 100% than I do.
