YES! I've waited for this moment at least 8 years!
My one and only question:
Can I share my games offline?
If I can, then I can use one account on 6 computers and allow all of my friends to play one game.

I tried the beta and basically if I want to try a game that I don't own, I have to ask for permission and the owner can't play it at the same time. Hence my "offline" question.

Dang, that closes the door for me. I'm mostly concerned about purchasing the game once and playing with friends offline on the same Steam account.
It has worked for years, but some games have disabled it.
If I have 6 computers at home in a LAN, why do I need 6 Steam accounts and 6 game purchases. That is just lame!

I see the benefits of family sharing. Your son/daughter moves to college and they take their computer with them. You can allow them to keep playing the family shared games.

Also this might be a nice feature for some of us to share our game for testing purposes.
Now, if you give me access to a game on your computer, can I download and install it?
Or is Family Sharing restricted to a single computer?