I have been using Coles Online sporadically for years now. Not because as Fred suggests, Im desperate (dont get that comment, desperate would be going myself!). I ride a motorbike, I also have cats.
Products like cat litter, cans of cat food, containers of milk etc (you get the idea) are basically a logistical nightmare when you can only carry limited amounts each trip. If i need a handful of items, i head up on the bike. If i need more, I do a large shop and stock up on the heavy/bulky items.
Once the initial set up and selection of products is made on your account, its relatively easy. You just add from previous shops that were delivered unless you need something different obviously. Never tried Woolworths, but with Coles you can pay by EFTPOS or credit card. Cash isnt accepted. You arent billed until the actual order is packed, so you dont get charged for any items not stocked.
You can also elect for the retailer to "replace" those goods they havent got with similar, i usually elect not to - my choices arent what theirs necessarily would be. I would rather go collect those few items myself later. The products have always been fresh, cold as necessary and well bagged. The drivers timely and polite.
As far as delivery, you select the day and window timeframe you wish to have it delivered. Shorter timeframe (for example 6am to 8am as opposed to 6am to 2pm), costs a bit more, generally though its about $6-8. With most cars, they would use that in petrol Im guessing. Never mind the stress of crowded shops and stupid self serve machines. Coles also usually offer delivery fee free timeframes.
I also had an operation on my hand/arm last year, and another on my lung the one before and i wasnt able to ride the bike for weeks at a time after both while recovering - without online ordering I would have been in the position of relying on others to take me and carry everything. I like being independent where I can, even when injured.
Its not for everyone, and sometimes you may prefer to go in person but it works for others like me. If you can only be home at certain periods then yes, to get the delivery time you want, you need to think ahead a little.
Oh and once ordered, you can change the order until approx the night before.
I loathe shops, and crowds. I love online ordering. I havent tried Woolies though.