Aye, it seems that basically you can only allow people to play games you have previously installed on their system.
This'll still help me and the GF out a lot, it basically means she only needs to log in and install my game/games once and afterwards she can play them whenever I'm not using it (or perhaps Offline mode, I guess we'll see how that works)
Can't say I'm surprised or even sorry that remote sharing isn't in there. The amount of nonsense that would come from that would be enormous probably. Constant sharing requests by people, support flooded with 'friends' who got their accounts VAC banned by cheating on their shared games, people 'renting' their libraries.
My only regret so far is the need for the game to have been preinstalled.
this is coming from a participant in the steam library sharing beta: you do NOT need a game pre-installed. What you need to do is sign in on the machine using whatever means you can/want to use (ie remote access to login) and then click authorize this PC provided it is running the latest steam client beta. You have 10 authorizations you can do. Also, to answer another question, no your account does not get cards from games you are borrowing that have them. Games utilizing 3rd party DRM/MMO games are NOT shared between libraries. What I have read that happens is if someone is playing a game from your library on a authorized PC and you boot up a game that the 2 accounts do not mutually own, they have 5 minutes to finish up what they are doing. At no point are you locked out of your games. Me and a friend (also in the beta) have yet to test this with games we mutually own. Sadly, all your games that use Steam as DRM (aka anything not running in dosbox/probably shared) are "locked" out if a friend wants to keep playing. Also shared are workshop subscriptions and other stuff. Further, expansion packs for civ V (using as a example because I know it happened) and other games that you own the base for but another library has, will download.