Tesco's self-checkout requires the customer to have a degree in nuclear physics, whereas Waitrose has a much simpler system! I love it when Sam has to ask me my age!
I prefer Waitrose, as the ladies really do ask me how old I am, but the ladies in Tesco have to put up with my wobbling around, putting stuff on the side, taking it off then generally getting on everyone's nerves, but Shirley is just a darling...
;0)