So far battery life seems better to me. I've had my s4 for about a year now and the kitkat update seems to have improved the battery. I'm running the google now launcher with location services on and the battery is doing just fine. Overall I like the simple Ui tweaks. Also not sure if this makes a difference but I've done this for the Android 4.3 update and, now, the 4.4 update. Before I even download the update I make sure that all my apps are updated from the play store. Secondly I restart my phone (the actual restart option). I then download the update itself. Restart the phone again, then install the update immediately. After installation is complete I again restart the phone. I've done this exact same thing for the last two updates and I did not experience any of the issues found in 4.3 and (so far) none in 4.4. Hope this helps.