I generally order my cats' food online, but sometimes if they're out of food, and I don't feel like driving to Sprouts, I swing by Pet Club.
Overall, I like Pet Club. It's easier to navigate than some of the big box pet stores, and the staff has always been friendly. They also have a customer loyalty program that allows you to earn discounts based on your spending.
The only two drawbacks for me are 1) the prices seem a bit higher than what I've paid at other places, and 2) their cat food selection is pretty limited.