Obviously AC isn't paying attention if he didn't know some Android phones have had this capability forever. I'm an iPhone owner, but I was quite aware of that. It always seemed rather pointless to me since T Mobile was the only big carrier in the US to support it, and they pretty much have had to push more consumer-friendly policies as a way of getting some attention from AT&T and Verizon.
What Apple did do by offering this with the iPhone 6 is get AT&T to follow, which is big news. No doubt Verizon will go along as well. One way Apple benefits Android users, even if they don't like to admit it, is they're better at pushing the big boys around for stuff like this. Another example being the agreements with Visa/MC/AXP for NFC, which will probably clear the way for Google to do the same (once they add support for one time use numbers which they should have had all along)
How useful wifi calling really is remains to be seen. If I'm in a place that has an AT&T wifi hotspot, would it force my call onto wifi? What if I don't want that, since it is more prone to packet delays that compromise the call quality? This is great if the cell is overloaded, but if the cell isn't and the wifi is overloaded I'm screwed. Given that I don't save any money this is probably something I end up turning off as being an advantage for the carrier but not for me. Really stupid that the minutes would be counted if I'm using my home wifi!
I suppose it doesn't really matter who is billed for the calls since minutes are no longer a scarce commodity. This would have been awesome about 10 years ago, but today it is meh. I could see it being really handy for those who have poor coverage at home or at work though.