In IOS5, there is no animation when popViewControllerAnimated is called.
this works on IOS4.
This is due to your RXCustomTabBar wich subclassing of UITabBarController.
But the IOS documentation specifies that this is not allowed.
The solution is to subclassing your RXCustomTabBar with UIViewController.
Thanks for this, I am away until mid Jan but if anyone wants to submit the changes to fix it I will merge them in.