I still liken it to using self checkout at a big box store.
The process is simple enough, depending on certain factors. If I grab 5 or so items, all very low level commodities, all with a working bar code, all heavy enough to activate the scale so the code will let me continue, I use a kiosk with no hidden issues, and either there's no line to wait for or I don't get behind someone else who has issues using it, I'll probably be okay.
But if I try to buy something that has an offered extended warranty the kiosk freezes up for an employee to come pitch it (that's becoming more prevalent every day, they tried to sell me a warranty on a $6 Disney Infinity Power Disc recently). It will do the same for someone to check my age for an ever widening range of products. If I try to buy something like produce it goes into the routine to weigh the produce, and that fails half the time. If I buy a greeting card or something else with no appreciable weight the kiosk is unhappy that it didn't sense when I put the product in the bagging area. About every 20th product I've tried to purchase at a kiosk has not been in the database and brought my transaction to a grinding halt.
All this, and I also usually have to stand in line behind someone who is totally baffled by the process when it's working smoothly, or who was foolish enough to try to complete a transaction on something that's tricky on a kiosk. Or buying five weeks worth of supplies.
What WDW is like taking out all of the normal checkouts and replacing them with self checkout kiosks.