To accomodate this decrypt() can no longer return false. If padding is enabled and the padding length is invalid (the only condition under which false was returned) an InvalidInputException will be thrown.
Also, previously, when encrypting, if the padding was disabled and the plaintext wasn't a multiple of the block size a E_USER_NOTICE would be issued via user_error() and then padding would be enabled. Now it's not enabled - an exception is thrown suggesting that you might want to enable padding and that's that.