UIPickerView and UIDatePicker are now resizable and adaptive—previously, these views would enforce a default size even if you attempted to resize them. These views also now default to a width of 320 points on all devices, instead of to the device width on iPhone.
Interfaces that rely on the old enforcement of the default size will likely look wrong when compiled for iOS 9. Any problems encountered can be resolved by fully constraining or sizing picker views to the desired size instead of relying on implicit behavior.
On iOS8, nothing should change and the height is ignored. On iOS9, the height should be honored and the picker should resize.