I am very impressed with the Jellybean OS.. I've noticed that my screen is now my main battery drain, even though I have it on the lowest brightness setting, but hey, it's not killing my battery nearly as fast as before the update when Android OS was my main battery drain.. I have yet to restart my phone after receiving the update and the battery life is phenomenal! And I've noticed that my running ROM isn't jumping up into the 700-800 range, so that helps as well..