Now that door-to-door supermarket deliveries are a thing (at least, they are here in the UK) it actually seems that a lot of items would just be more convenient to order on a subscription basis. For example, I'm pretty much always* going to need toilet paper, soap, shampoo, deodorant, toothpaste, tea bags, salt, pepper, etc. at about the same rate as I need them now. None of those things will spoil fast enough for it to be a problem if they're not delivered exactly when I need them. I would be delighted to just not have to think about the essentials and leave grocery shopping for the more interesting, impulsive decisions. These buttons seem to be just for the former, though. In other words, I'd rather not have the button OR the auto-running-out-sensing thing when a regular order would just be easier all round.
I'm annoyed they haven't closed the PID loop to track how many oz of mouthwash I consume, or use, per month, so it could predict how often to ship me various sizes and quantities of mouthwash.
Also being individual item oriented every time inflation leaves its mark and bottles shrink in size, my subscription is cancelled and I need to make a new S+S for the "new and improved" one oz smaller bottle. And every time the mfgr decides to play games with 2-pack vs 3-pack of bottles, I gotta resubscribe again. Really annoying.
What I want from amazon is a web interface of "based on order history I seem to be using 412.345 oz of mint mouthwash per year and amazon predicts I have 20.001 oz on hand (click here to update quantity on hand) and to meet our guarantee of you having 2 weeks supply on hand at all time we're shipping you our current mint mouthwash best deal of two bottles in one box" or whatever.
I get a pretty big S+S box every month. I have not automated down to weekly purchases like toilet paper but inevitably it'll happen some day. I wonder if they'll ever have a standard reusable stackable shipping crate like peapod food containers. That must be cheaper than all this cardboard.
I like the idea (diapers and UHT milk packets) until they tell me they can't fulfill the order every once in a while (or fulfill it significantly later). I get an email (and not in time to order a replacement elsewhere in time) and have to go about ensuring that I have enough.
If it's not reasonably reliable, it's not really worth subscribing to.