By my understanding, only the HTC First will have Facebook's lock screen. Without that, Home is just another Launcher.
The upside of HTC First: will be the first HTC device to have native Android UI - if you turn off Home.
The upside of HTC First: will be the first HTC device to have native Android UI - if you turn off Home.
Home is more than another launcher, though. In some ways it defines a new class of application software for Android - a cooperating suite of apps, with a coordinated set of interfaces.
There is no way for an app that expects to be installed normally, using the normal system of permissions, to change out the lock screen. In practical terms, Facebook could not insist their users root their phones. For some debugging tools, that's much less of a problem.
There are "pseudo lock screens" but those are very hacky.
How soon we forget. HTC did make a little phone called the Nexus One. Prior to that they also made the T-Mobile G1 / HTC Dream.
That being said, I don't know if the HTC First will really have a native Android UI underneath. It could just as easily be "Sense themed to look AOSP" like the (US) T-Mobile G2. That probably depends on how much Facebook cares about what's underneath.
Edit: Apparently HTC's OpenSense SDK includes lock screen APIs (see http://www.htcdev.com/devcenter/opensense-sdk/lock-screen/lo... ). That seems like another argument for a Sense-derivative.