I also had problems with battery life.
but after reading this thread, i turn the flight mode on and the wifi off before taking the playbook in sleep mode.
now the battery life lose overnight only a little bit of capacity.
I noticed that Wi-Fi Sharing also consumes a lot of battery when Wi-Fi is enabled. Apparently, there's a lot of network communication when this setting is turned on. BUT I don't have any data to prove this... for now.
Also "Application Behavior -> Showcase" must consume more battery since all apps are kept active and never paused on the background. So if you have many apps running at the same time, this should impact.
