Every software update Apple released for the past months seems to cause enormous issues with at least one of their devices. Unbelievable.
Well now there are more possible update scenarios to check. The number of devices supported has increased. Then the iPad can be Wi-Fi only or LTE and older devices have CDMA or GSM versions and then you have updates through itunes or over the air and finally there is the history of the device (was it registered to different itune accounts in the past).I don't want to do the math but there are a lot of scenarios. For example on a recent update there was a specific problem that only happened with iPad 2 GSM with an over the air update. They should check all of these of course but frankly I am not surprised some things are falling through the cracks.