It will be interesting to see if Sainsbury's do introduce a 'scan as you shop' option.  In other parts of the country, Waitrose have had that option for well over a decade and Tesco, not quite as long but for a good few years.  I believe Sainsbury's are now introducing it into stores too.  None of the large Tesco or Waitrose shops I have been to since moving to London last year have had the scanners in store.     Scanning as you shop is a huge time saving compared to a 'traditional' shop - if only because you handle any item only once - off the shelf, scan, into your own shopping bag.  Compared with item from shelf into basket/trolley, item out to be scanned at checkout, then into own bag.