Yesterday I used Apple’s continuity feature, it was not something I intended, I just received a phone call while using my laptop, and my phone was somewhere else in the flat: the Mac offered me to answer the call. Using a feature, not because you intend to, but because it is the natural thing to do is the sign of a good design. While the sound quality was not perfect (I was asked if I was on the move), it was enough for a call.
I really hope that more applications adopt this model, an applications that triggers notifications on many devices, regardless of the device you are using is very annoying. Skype is pretty bad in this respect: an incoming call will make all devices ring, even after I picked up with one of them. There is a certain irony of having a call disturbed by the noise of the ringing of said call.
It is interesting to see that routing a classical phone call through my local area network is a new feature in 2014. While IP telephony is widely used, it is mostly deployed in corporate network, with a separate network infrastructure to support it, reliability and integration are still pain points. Most chat and video conference system run on proprietary protocols. In that respect, Apple’s approach of building improved services on top of the telephony network instead of trying to replace is interesting: you can see it as a political move to not anger operators, or a way to use a reliable infrastructure for voice.