I used them early in the pandemic for months, but switched to Freshdirect since the latter has up to date and accurate online stock. What's in your online cart is what gets delivered. With Instacart, because they deal with a bunch of supermarkets (which you choose from - the competitive advantage) you get a 'shopper.' In my experience the shopper couldn't find 30-50 pct of the items. Non organic tomatoes replace my organic tomatoes. A bunch of items just not found and price refunded. Some obscure Italian olive oil I put in the cart is replaced with a completely other brand and bottle size. All this, and the app sends me notifications asking me to approve the replacement. Ok, but the shopper is shopping for others, too, and so the notifications for me to approve happen every 3, 5, 8, 10 minutes for 45 minutes.

Not sure how it is in other locations, but in mine, the business model of loosey goosey stock quantities doesn't work for me as shopper, and it's probably too complicated for them as a business to keep close tabs on what's available.