1. A thermostat comprising: a housing having an electronic display disposed thereon; a rotatable user-interface component configured to track a rotational input motion of a user; and a processing system disposed within the housing and coupled to the rotatable user interface component and to the electronic display, the processing system being configured to identify a setpoint temperature value based on the tracked rotational input motion, the processing system being further configured to be in operative communication with one or more temperature sensors for receiving an ambient air temperature, the processing system being still further configured to be in operative communication with a heating, ventilation, and air conditioning (HVAC) system to control the HVAC system based at least in part on a comparison of the measured ambient temperature and the setpoint temperature value; wherein said processing system, said electronic display, and said rotatable user interface component are collectively configured such that each of a first mode of operation and a second mode of operation is provided, said first and second modes of operation being in effect at different times, wherein, during said first mode of operation, graphical information is displayed on said electronic display that is representative of said setpoint temperature value as identified by said processing system according to said tracked rotational input motion of the user, wherein, during said second mode of operation, an arrangement of selectable menu items is displayed on said electronic display, said tracked rotational input motion of the user causing different ones of the selectable menu items to become visually highlighted as said rotatable user interface component is rotated, a user selection of one of said selectable menu items being established by a user confirmation input provided by the user while that selectable menu item is visually highlighted, and wherein, during said first mode of operation, a positive-reinforcement icon is displayed on said electronic display when said setpoint temperature value as identified by said processing system is determined to be in a range associated with improved energy conservation.