I'm pretty sure it's brilliant for FPSes.
I'm pretty lousy at FPSes anyways. Metroid Prime for the Wii was the only "FPS" series I really liked.
As for the controller itself, I'd have to try it before forming an opinion. The video was helpful, though it seems like he was using the triggers to shoot and interact, instead of the face buttons. I am curious to see how one would actually use those...I'm also surprised that no one pointed out how TINY the controller is, I dunno how the size would affect gameplay.