I have been using the service for about two years. While it saves a ton of time my wife and I decided to cancel the service once come the middle of January.
1) You don't pay the store pricing (which we knew going in). If you were to go into the store and pick up something that is normally $1, Shipt is going to charge you $1.10-1.39 for the same item. I know they need to make money, but it seems the pricing has been creeping up, overt the last six months. Paying the $99 for the year for service, then the extra money on the items, plus a tip for the shopper/driver, it was getting to the point it would be more cost effective to go do the shopping myself.
2) 3 of the last 5 times we have ordered the service has been down. The person has shopped in the store, headed to the check outs, and the credit cards Shipt use won't work. So we have to reorder for another day. Shipt doesn't seem to care about this, won't offer a credit because of non delivery. This is the main reason we are leaving.
3) The shoppers/drivers can be hit or miss. Most that have done shopping for me have been great. A few though, stink. One got nasty with me because I didn't respond to a text within 30 seconds of her sending it. If they don't have something they are to contact you to see if you want a different item, or skip it. They also will ask if you want anything else added to the order when they start.
Overall, it did save time by not having to go to the store and shop. Especially this time of year.
Here Walmart started doing home delivery for $98 for the year, and the price you pay for delivery is the same price in the store, which is great. Now they won't contact you if something is out of stock. They will just substitute for a like item, which can work in for favor (ordered the Walmart version of something and got the national brand instead at the Walmart price). It can also work against you (order the national brand, they don't have it, they will sub the Walmart version, but you still pay the national brand price). You can choose to not have them substitute anything or just some items when you go to check out. Been using it for about three weeks now (first two were free), so far so good.