Oh, I like it very much and it's really useful. Or could be if it was better implemented. For single portraits in M mode, it's already quite nice today. Since more than 99% of my shots are taken in M mode, I don't feel the exposure metering annoyance. But a quick toggle between multiple recognized faces would be nice.
In essence, Fuji should bring the new AF-C Tracking mode algo to face detection. It's the same technology (pattern recognition), so it shouldn't be much of a problem really, at least in theory. That would boost face detection performance tremendously.