I've used a microwave which has one dial. You can turn it clockwise or anticlockwise to add/remove cooking time, which is fine.

The designers thought it'd be good to allow pressing the dial, as if it was a button. Pressing the dial set the cooking time to 30 seconds and immediately started cooking. A one-touch interface, how useful!

The only problem was that it was difficult to press the dial without accidentally nudging it clockwise or anticlockwise. Nine times out of ten I managed to turn it anticlockwise, which set a time of 95 hours or thereabouts - and began cooking.

I hate to think what may have happened in some people's houses where they've done this, not noticed that it said 95 hours and forgotten it was cooking.