I was forced to wipe and reload due to an entirely different issue. I actually think my battery is lasting longer. I concientiously close my unused apps though.
With 4.2, exiting an app by pressing the home button no longer necessarily closes an app. When you double click the home key, you can see in the task manager which apps are still running. Some but not all of those may be pulling power from your iPad. To truly close them, you must first double click the home screen to bring up the task manager, then press an app icon until it goes jiggly (like moving or deleting on the home page), then press the little minus sign in the corner. The app will disappear from the task manager, and it will be closed.