The addon will reduce cycles render time generally between 3 and 5X, but this can vary dependant on scene.  More complex scenes with lots of material types and complex lighting will be reduce much more than extremely simple scenes that already render quickly without the addon.

In addition to reducing actual rendering time, the addon also simplifies render setup, post production tasks, which save massive amount of time.

And finally of course, the Temporal Stabiliser allows you to remove flicker from animations that would otherwise require much higher samples and rendering times!