I alo had a lumia 950. It does not have face recognition, it has an iris scanner. An infrared light lights up your eyes and then the camera makes an IR picture where it analyzes your iris pattern. The reason it didn't work well is that your eyes had to be open (no squinting, like in bright light), close enough to capture a precise image and in exactly the right spot for the zoomed in camera. I eventually learned a gesture that unlocked it semi-reliably, but it was basically holding the phone right up to my face in the exact right spot.

Now that I see how apple is doing face id I think it will work more reliably ... eventually. I doubt they'll get it right on the first try because this is the kind of feature that has to bake in the real world (like apple maps). Still, they may surprise us like they did with the equally hard touch id feature.