The Epic 4G update seems to have caused a lot of issues with battery life, and it looks like flynlow from the Android Central forums may have found the answer why. After various attempts to fix the problems, both by Sprint and flynlow himself, he stumbled across a very interesting and pretty relevant issue -- The Media Hub update brought a DRM content service along with it, and that service is keeping his Epic 4G from sleeping properly. To be clear -- I'm not knocking Samsung for the DRM service, they do need to protect their assets. And the fact that it took some digging to see the issue means the DRM is pretty seamless to the end user. It does appear that some bug fixes need added to the list though.
Having been a HTC Hero early adopter, I know exactly what a process that wake-locks the phone can do. If you're having issues with your battery after the update, do yourself a favor and check out the thread and try it for yourself. [Android Central forums] Nice work flynlow!