I know it varies by location, but I have been using self checkout for years.
There are always more self checkouts open than there ever where staffed lines. I don't get in the line that has someone argue over checks or coupons, when a spot opens up the next person gets to start. If I only have a few things I don't need to spend 25 to 20 minutes in line like I did before self checkout.
Other than a couple years of growing pains, self checkout has been a massive improvement for my general shopping experience. The fact that so many trips are for a few items probably impacts that, but even when picking up a week's groceries I prefer self checkout.