So I have been in the Steam Family Sharing Beta for a couple of weeks and I have to say that the experience is not what I and a whole load of other people were expecting. There are some technical issues, which can be overlooked but behind the whole system there is one massive flaw: if you are not able to access the computer you want to share with, you can't share, full stop. So either you need to have physical access (to log into your account on that machine and activate sharing), remote access (remote desktop, Team Viewer) or by giving out your account details. Either way, to use family sharing on Steam you are required to type your login data into a different machine which is a massive security risk in my opinion. I might trust my family members and close friends, but at the same time that trust obviously won't be good for anything if their machine has been compromised by malware.
I feel that this does not reflect what Valve had announced at the start and if you compare the language of the current version of the family sharing sub site with the version that was up back in September, there are a lot of changes in the text. Simply put: the original version was quite misleading and even the current one still doesn't spell it out: you have to share your account details with someone to be able to share your games.
I do hope that, with the service being in beta, Valve will listen to their customers. The feedback on the official family sharing forums is overwhelmingly negative and while the idea is obviously brilliant, the implementation does not live up to it. It's a clumsy and roundabout solution that is creating a big security risk to solve a problem that already has a very easy solution.