Adapted from UX Design Edge.

• Affordance - does the UI allow user to predict future state.
• Expectation - are triggers labelled and/or adopt universal symbols (i.e. the right facing triangle for 'play')
• Efficiency - the number of triggers needed to reach a desired state is the absolute minimum
• Responsiveness - the UI provides instantaneous feedback on whether a trigger is being processed and/or a state has been changed.
• Forgiveness - a user-induced error can be caught and corrected and/or undoned.
• Explorability - (IMO not relevant to physical UI) users can navigate throughout the UI without unintended consequences, or of getting lost.