Does the user sync plugin add users to all of the sites?

So I have a network of sites and I wanted to have it where they login to the main site and automatically have access to every following site in the network.

I hope it works this way but the way it reads is that once I activate the plugin the only way I can add them to the site is to sync every day to add the additional users.

I guess I am looking for clarification. If that is the case then I guess Ill just have to use the fb registration from ultimate facebook plugin (its awesome)

Well any guidance as to how to do this would be great.

Thank you for all of the help