My local Target has a self-checkout lane with four or five machines.
Of course, it's not as important as the ones in my local Walmart because whenever a line builds up at the registers, they call one or two other staff over to open new registers. Meanwhile, at Walmart, it could be a really busy time of day and they have 2 of the 20 registers open with no extra staff to call over.
I don't have as big a problem with Walmart as many here (or my wife), because I also don't pay attention to the typical difference in clientele and there are certain things I know I can get there cheap. But the customer service is a completely different experience at the two stores.