Well, this has its bad and good side.
Impressive for a game, and if used properly can produce some astonishing results.
On the other hand, each NPC would depend on one actor, so that could lead to some very poor performance. And many actors would have to be envolved, taken the number of NPCs (if they don't want to have 1 actor's face on 10 NPCs, that is). Of course, that means more money spent, and if they want some celebrities appearing, they'd have to pay mucm more - probably as much as if the real movie was made. And that is, of course, very demanding, for every gaming company.
Also, I'm nitpicking, but all those lighting, shadows and textures would prove (and are proving, in this video specifically) to be quite weak. I mean, you can have very realistic facial expressions with motion capture, but if you ask me, the whole image is ruined by poor effects that are used (again, just in this video).
Overall, it is a nice thing, but I'd stick around with those "classical" techniques of showing faical expresion - such as those used in Bioware' games nowadays. I'd stick to them, at least until this thing gets improved more.