I have just had my flex mobile app rejected from the Amazon Appstore because when you rotate the device (android), the view does a temporary resize which causes a rectangle of the app background color to display. If you slowly turn the device, you can easily see this strange resize behaviour as it goes from portrait to landscape or vice versa.
I have autoOrient true. This can be reproduced by simply creating a default Flex Mobile Project with a Tabbed Application (Flash Builder 4.5.1 with Flex 4.5.1 SDK) and trying it out on an android device. Note that the emulator will not show the problem.
I have tried to figure out how to stop this behaviour. It appears to be related to having the TabNavigator views with width and height of 100%. Having a fixed size stops the ugly look during rotation - but I'm unsure of what sizes to set them to for fear I will end up with something even uglier on a device I can't directly test on.