For rooted users I have started using
Greenify and I have been very pleased with the results so far. It is a battery saver in that it will put your apps to sleep when they are not being used so you don't get a lot of back ground apps running, eating battery. The pro version will let you do system apps like Google Now to save even more. I don't use a lot of location services and such so putting Now to sleep is no big deal for me.
I have gone from a roughly 7.4%/hr battery drain down to a 3.2%/hr drain over the past week. Easily getting 18hrs with 4hrs screen and 40% battery left with the exact same usage as before. One day I went 39hrs with still 15% left.