One of the features that had gone unnoticed by not being mentioned but that I consider important is that Mavericks makes use of the ambient light sensor to detect movement in front of the Mac and thus prevent the computer from going to sleep.
At first some developers pointed out that the camera was probably the manager in the background of this task but it was quickly discovered that this was not exactly the case and it was the light sensors that were in charge of this task.
I can think of different uses for which Apple have thought of this solution to use it instead of the camera and it is that surely the battery consumption of this sensor is less than that of the camera in addition to that many times we spend long periods of time in front of the screen pointing at other things or performing parallel tasks without touching the equipment, but from time to time we look at information on the screen with a program open, so it would be a nuisance if the screen turned off and went to sleep.
The sensor is already used to adjust the brightness of the screen to ambient light, but the new operating system provides a different purpose, monitoring changes in light that are analyzed as "movement" and this in turn manages to restart the downtime accordingly. According to tests in The Verge, they are confirmed in two different computers with Mavericks installed, and it is that after covering the camera, but not the light sensor, we have been able to delay the sleep mode when changing the ambient light conditions.
More information - The activity monitor brings several improvements in Mavericks
Link - The Verge