In an Ionic 2 project or any Cordova project for what I now, beware if you set below key in
<preference name="StatusBarOverlaysWebView" value="true"/>
ion-navbar heigth will change and
ion-buttons directives will not be vertically aligned.
This is an bug that did cost me 4 hours to debug and since that is a completely unacceptable amount of time for a simple 4px styling issue, I wanted to share this.
Another good ressource to find answers to your Ionic 2 questions are the official Ionic Forums.