I have experienced a faster battery drain after the KitKat update. I have perform 2 Factory Resets: One from the settings menu, the other using the alternate method. I am using the same apps I have been using from almost beginning of time. I do not root. Same thing happened with my Samsung Fascinate after Gingerbread update. There may be subtle manufacturing differences with our phones, such as a different chipset used that may be from multiple vendors, something. It could not be explained.