I didn't use it that often, mainly because I had Twitter set up to automatically post tweets on facebook (which, of course, would result in double posts on facebook)...
I did find a sweet 3rd party app that will post simultaneously to Twitter, Facebook, and LinkedIn (if you like). It's called
Multishare. It's free and it's well integrated with the system, appearing whenever I choose share from an app (browser, photos, rss feed, etc.). In the preferences, you also have the option to shorten links, share to clipboard (for pasting elsewhere, e.g., OneNote), and the Facebook integration lets you choose the audience (friends, public, etc.) at the time you post.
MultiShare | Windows Phone Apps+Games Store (United States)
I would prefer to have the functionality built in to the OS, but perhaps this is one of those things they felt 3rd parties could better maintain, relieving the Microsoft team of the burden of keeping up to date with changes on Twitter and Facebook.