I can pack stuff in my bags with no rush (there's usually no line for self-checkout, since not everyone uses it), just scan the bar codes for products that have them and pick from a menu/search for those that don't (e.g. freshly baked goods in paper bags). Then, I can pay with my card, or sometimes have to verify my ID with the shop attendant when buying something like energy drink.
Smaller stores probably won't have self-checkout any time soon and some stores like Lidl don't seem to have it either (the prices there are nice, but bagging your products always seems so rushed), but where it's available, it works pretty well (like Rimi, Maxima).
I really appreciate it being optional, though, as well as having the more traditional option with shop attendants and the small conveyor thing.