fullscreen was broken in 1.5. i created a fix as a subclassable RootView, with static convert_point and convert_rect methods which work the way they were supposed to.
i only ever tested on ipad, iphone might behave a little differently, but sounds like you had similar issues.
I apologize this is poorly commented, but the example should show how to use it. I also found the first time the kb appears, the frame is sometimes wong, so you may need to show/hide/show the kb, see near line 95. Also, if memory serves, the frame passed to the callbacks was broken in fullscreen for some orientations, so you have to use the get_keyboard_frame method in this class.