I don't know about your phone but on mine the prevail, it is apps running in the back round that eats up battery. Things like roaming or searching for service too will drain the battery too. You can go into menu/ settings/ applications/ running apps, it will tell you what is running. Some apps like facebook on my phone run all the time so I don't use the app I just use it off the browser or internet, only use it now and then. They also have apps out there to control running apps. On the prevail I also use titanium backup to freeze things I dont use regularly and then defrost when I need to use. The update might have changed some things that run differently that is drawing battery down.
Like I said this is what works and how my phone performs, every phone is different though. As for running apps it should be the same on all I would think. Hope this helps to get you going in the right direction.