Be Careful: the ‘pursuit of delight’ can be more for the designer’s entertainment than the customer’s satisfaction.

In many cases the customer isn’t looking for delight; they just want to complete the task and get on with their lives.

‘Delightful features’ can be exasperating because they delay the task for no apparent reason.

For example, the pumps at my local gas station make me sit through a 4-second production to announce that “we’re lowering your gas prices!” It might have been notable the first time, but now it pisses me off and I wish that it would stop.

Also, don’t forget to assess the design with respect to the other people who regularly interact with the vending machine. For example, the person loading the products and retrieving the money.