The wpseo_title filter allows customizations of the title tag, but they aren't used on the OpenGraph og:title output. It would be great to sync any customizations made to title and og:title.
I quickly patched this by changing Line 146 of class-opengraph.php to:
echo "<meta property='og:title' content='".esc_attr( strip_tags( stripslashes( apply_filters( 'wpseo_title', $title ) ) ) )."'/>\n";
Thanks for taking the time to put together such a great plugin Joost.