We actually had a program in some of our stores a few years back called Scan & Save. You picked up a hand held scanner along with your shopping cart when you entered the store. You scanned your items when you placed them in your cart. Then at the checkout the cashier only had to deal with payment and any items that were sold by weight. It seemed like a good idea, but it really didn't work out well. Too many issues and too many folks who couldn't seem to figure out how to scan things with the little guns. The scan guns weren't all that durable, and you can imagine how often they got dropped by customers.
The company has done some experimentation with RFID as well, but that hasn't really gotten off the ground - at least so far. I won't identify my employer except to say it is a major national retail chain. In theory I like the RFID idea. The difficulty is in the implementation.
Another technology we have looked at are electronic shelf tags. Instead of the paper pricing labels that have to be replaced every time a price goes up or down and twice when something goes on and off sale the tags would be electronic and display prices on a little LCD screen. Price changes would be implemented instantly by wifi. While that has potential it has to this point been too expensive to be cost effective.
We do have self checkouts in some stores, but not in all of them. The older machines were problematic. The newer ones are much more reliable. Some people love them. Some hate them. I use them for my personal shopping wherever available unless the line is longer than for the manned registers.