http://www.walmart.com/search/search-ng.do?search_query=ensu...
http://www.walmart.com/search/search-ng.do?search_query=cent...
If it is then I can't figure out how to use it. Those were just the two items I would like to purchase and typed in first.
Regarding the "click a button for what I want, then open my door that same day and see my items sitting there waiting for me", that's not true for many places. I live in a tech-focused capital city and shipping is at least 2 days for Prime but I've had it take much longer (yes, for items sold by Amazon). I regularly see Amazon do the "our shipping carrier handed your item to USPS and we are no longer responsible for how long it takes" routine and it is completely unacceptable.
Once they get the site-to-store thing right (in it's current state you are correct, it has flaws) then they should offer some kind of large promotion to encourage people to register and use their service one time. Right now I'm hesitant to register and start shopping with Walmart, I don't have a logical reason for this though.
Real innovation will be when I can order and pay online, then send out my autonomous vehicle to walmart, then one of their employees will put the items in my car and the car will drive home and text or email me when it arrives. That's probably 10 years away but it will happen.