This way, you don't have to log in to your friend's console, nor share your account details. It's just a matter of adding them to your family friends list. And it'll also work with games you buy (cheaper) at retail.
I know, it's a little smoother and safer than the PS3 solution, for sure.
I thought it was a megaton though. I was thinking you could buy a game, share it with 10 people and all 10 people could play at the same time. This would have probably swayed me to get an XBone to be honest because, as others pointed out:
Get a group of 10 folks on GAF, each person buys 1 game per month, everybody plays it. In 10 months you have 10 different games and all it cost you was $60 bucks. I would be okay giving up my consumer rights to resell my products for that kind of a deal.
Sharing with just one other person is nothing new though, Sony has been doing. This is just a little smoother, that's all there is to it. Like I said, people used to have dummy accounts to share games on GAF when you used to be able to share it on 5 different machines.