Target and Whole Foods have minimal oversight and the machines are efficient and permissive. Delightful!
Costco has machines that are not permissive and complain a lot. I find this odd, considering that Costco is members-only and double-checks everyone when they leave.
IKEA has one employee per 1-2 machines. The machines are terrible. The scanners are unreliable, and the machines are slow beyond belief. I suspect they’re accidentally quadratic (with a bad constant factor), and I’ve had to pay part way through and start a new transaction to make forward progress at a reasonable rate. The employees might be there more to babysit the machines than to deter theft.