Coming from a Nexus 6P, I HATED the placement, but as others have said, muscle memory is a weird thing and I adjusted pretty quickly and along with a thin case I have which has a slight ridge around the FPS, it's become really easy.
I had the face recognition active, but I hated when I just wanted to look at my lock screen to maybe swipe or delete some emails without getting into the phone and it popped right passed the lock screen, so now I just use the FPS and I'm happy with it.
All that said, I do actually think it should be centered like the Pixels...