This plugin has lots of features which you can turn on/off and configure.
Therein lies the problem. Because it has so many modules (features) it contains lots of bugs.
If you ever have a problem with your WordPress.org blog this should be the FIRST plugin that you deactivate to see if it is the problem.
I don't use all the features but it does contain Vaultpress backups (not free), a Contact form, Custom CSS makes updating the theme's css a breeze and Facebook publishing works fairly well (sometimes it doesn't publish to fb and one has to reconnect it).
All in all I recommend it but with a warning that it conflicts frequently with other plugins. Automattic has continued to improve upon it and perhaps someday it will become a quality plugin or be integrated into the WordPress core files.