First of all, there is the Updated Energy History View that enables Nest owners to see exactly when and for how long their heating or cooling (HVAC) systems have been turned on and off over the past 10 days, in addition to whether their energy use increased or decreased compared to the previous week, as well as the probably cause of that change.
As for Airwave, it will help optimize the use of the fan instead of A/C when Nest is set to cooling in order to save energy while continuing to keep temperature down. Airwave works by adapting itself to your home; turning on automatically if the humidity is low, which in turn results in a lesser amount of time which your compressor is left on.
The update user interface also makes it a whole lot easier to navigate through, while DIY enthusiasts will be pleased that it is even easier than before to install, since Nest devices will now come with a revamped backplate and wire connectors.