Duo competes with Facetime, except it's not integrated in Contacts and I can't imagine why. Duo and Facetime don't compete with Skype because they don't have the IM part which is a very important component of Skype. I used it for all these years as an IM client (business or friends), less as audio and rarely as video. But video is always the least used form of communication. Still I'd like to see some global usage stats of Skype: minutes by chat, voice, video. My customers, friends and I could be the outliers.