Other ecommerce sites frequently have so many additional/hidden charges that I would never want to click "buy" right from the item page. I abandon so many carts when I get to the checkout page because there's $20 in shipping charges on a $8 item, or they've tacked on a $5 handling fee, or they wait until the very end of the process to tell you that the item will ship in 8 weeks.
In my experience the price shown and delivery time estimate is always accurate, and as a Prime customer the delivery fee is included in your subscription
Just because it is easy to return things doesn't make me feel good about doing it - it is such a waste. Maybe I should look at it as creating jobs.
I've never used it for other things though, even as a Prime customer.
My main issue with it is I use different delivery addresses, sometimes to work, sometimes to an Amazon Locker, rarely to home as I'm never in.
it's probably because I don't use 1-click that often, because it is rarely 1-click, which leads to me not using it very often
(I use normal buying constantly though)