I really like the fact that you can make multiple lists and set up categories for the item to help organize your shopping trip. The Alexa skill that allows us to tell our Echo what to add to which list is a nice addition. If I realize I am about to use the last of the eggs in the kitchen where the Echo is listening, all I have to do is say "Alexa, ask Our Groceries to add eggs to Wal-Mart".
I knocked off one star for the implementation of the ad-free option as an in app purchase. To share lists with my wife (one of the main reasons I got the app in the first place), we have to both sign in with a "master" email. But since we each have our own Apple IDs and they implemented the "plus" option as an in app purchase, it is not eligible for family sharing. That meant to hide the ads for both of us, I had to buy it twice. I did it because I like the app and I want to support the developers, but it seemed like a deliberate choice to make it more expensive.
Hopefully my contributions will help the developers continue to make improvements to the app
Hereford Farmer about Our Groceries Shopping List