Recently let me Sam's Club membership expire from all the hype I had heard about Costco. While I the variety of items is fantastic and prices are not bad. The checkout lines are absolutely horrible, lines running half way the store. It tempts me to cancel my Costco membership and go back to Sam's Club. Recently they (Sam's Club) developed a "Scan & Go" app for android (maybe IPhone as well) where you scan the items barcode you want, and when you are finished you pay on your phone. Then show e-mailed receipt to individual that reviews receipts as you are leaving and you skip the horrendous checkout lines.
Costco, you need something like this, sooner the better.