I've been using Snapstream's BeyondTV for several years. I've got 3 BTV boxes in my house. I tried to set up a Myth box one time. It was too complicated for me. I absolutely dread when stuff doesn't work and I have to go online and figure out how to make it work. I've still had to do a little of that with BTV, but overall it's been pretty good. It does lock up now and then and my relatively recent addition of a Hauppauge HD-PVR box has been an absolute bust (love the rest of my Hauppauge hardware, but the HD-PVR requires daily, sometimes hourly, reboots). Anytime BTV misses a show I have to hear the wife say, "Why does it always mess up on my shows?" So it happens, but not so often that the wife insists on a change. For important stuff, I set up recordings on more than one box. They're all networked so I can watch any show on any TV. I also have a HD cable STB PVR that I never use because the UI is awful. I just control it using the previously mentioned HD-PVR under BTV.
If there were RFID tags on all of the items, you could bag them yourself as you selected items from the shelves. Just add bags to the carts. It would take almost no extra time. Checkout would be a quick scan of the cart and payment processing.