I've been wanting to get a FFC for a while now, but I'm running ICS passion, and if ffc doesn't work with it, then it is pointless...
The ICS Pasion thread state it does work, and they have the face unlock part - but the issue is the FFC cams we have are lower image quality than on newer ICS based phones so face unlock isn't as good.
I have a FFC in my Vibrant, I rarely use it now that I have the Power Button mod to take pictures with the better rear cam. (I'm using Tard 2.1 Rom - based off Bionix)