Overhere, there are not a lot of supermarkets offering self service, but the ones that do, have a perfect system.
You get a hand scanner, pick your groceries, scan them, put them in your bag and pay by card at the self service till after putting the hand scanner back in it's slot. There are scales for weighing vegetables. Every once in a while you get a check to see if you're not stealing stuff, unless you're buying alcohol, then they come and check you anyway. Seems to work (and the rate of stealing will probably be the same as when using normal stuff) and it saves me a LOAD of time. Sometimes i see people waiting for a regular till, which are still there when i'm ready with shopping and leaving the store :)