The integration with Facebook makes it easy for users who do not use Google Calendar or Apple's iCalendar application (or those that don't have access) as well! It also syncs easily across different devices such an Android phones/tablets & iOS iPhones etc., which other solutions cannot say they provide out of box..
Maybe there are more features I'm missing but so far this one has been very useful indeed in my day job helping run our team meetings schedule using google calendar + FB groups - no longer need any additional addons like Anylist Pro from previous versions now all can be done natively within Calreply app itself!! Definitely would recommend if you're looking at integrating your teams' scheduling needs into facebook group chats / social media platforms instead off traditional emailing methods!