There was some testing done on that at certain stores last year. The last report was it not very good, from A user here who was a test store. Other retailers are dropping self checkout lanes too.
Here is a link to a recent story:
At least one store in my District has them. I don't see how this is a good idea, considering the amount of shortage it would cause. Grocery stores can get away with it because they don't have anything worth more than $20 (except certain alcohol). It also wouldn't decrease lines at the checklanes, considering most guests can't figure out where to swipe their card on the normal card readers. :wacko: