I have been ordering online with Coles for about three years and I have only had a couple of major problems. Once they left out more than $20 of products. When I complained I got that amount credited to my next order plus free delivery.
Another time I had ordered four cartons of soft drink because it was on special. When the delivery man didn't bring it he admitted he had just delivered a large order of cartons and he must have given them 24 instead of 20 i.e. he had given them mine.He said he would tell Coles. I phoned up Coles and got credited for them plus free delivery, went to the website reordered them and they got delivered the next day.
In the last 18 months to two years there has been a vast improvement with only minor problems.
Delivery here is $7 or $9 on Friday or Saturday. That is cheaper than bringing my groceries home in a taxi.