There has been report that the Epic 4G's latest update seems to have been caused a lot of issues with battery life. It also looks like we have information to the reason why. After various attempts to fix the issues, both by Sprint and other epic users, they 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 and peacefully. It does appear that some bug fixes need added to the list to take care of these issues. Hopefully they fix this issue before the rollout of the Galaxy Tabs. There hasn't been word from Samsung whether this would affect the Galaxy Tab as well.
Having been a HTC HD2 early Android 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 keep in the know about the progress that is being done to your phone.