Because of security reasons on password fields during login or sign-up flows Apple's iOS8 will reset your non-default Quicktype keyboard to iOS standard. The result: A users' flow will be interrupted and it may take her a couple (or more) tries to get the password right.
If users may need to re-try they might even leave the app and come back at a later time. The result will also be that your conversion rates will start to look different from what it used to be in the past. You may see more app starts and closes, more switching between screens during login or sign-up.