Facebook Home for Android just went live. In addition to using it on the newly available HTC First, you'll be able to get it on "select" Android phones including the HTC One, HTC One X, HTC One X+, Samsung Galaxy S III and Samsung Galaxy Note II. Go get your homescreen on. [Google Play]
Just tried and uninstalled. Widgets are no where to be found. Notifications are hidden. On the SGS3, you can pull down to get notifications when they're hidden by an app, not sure what it is like for other users.
Since the ecosystem is completely derailed by Facebook, other devs, especially ones that make widgets and notifications, are completely shut out. Android customization is virtually gone.
If you're married to Facebook, and that's all you want out of a smartphone... go nuts. If you want to keep the features you love and enjoy today, stay away from Facebook Home.