First, the grocery store I frequent most doesn't have self check outs but I do use them occasionally at other places. Second, and I say this with the most delicacy possible, as I know some people will likely take this with offense, but generally the experience I have here with people working at grocery store check outs is infinitely more pleasant out west than it is in the midwest, south and on the east coast. I won't go all out and say people are nicer here because I'm not sure that they are, but I will say that people seem to me to be much happier here than in a lot of other places I've been and it seems to reflect in their attitude to others.