Laggy and unusable? I would love to see a video of this. I often hear people complain about lag on devices I own, like the 6 plus, and I think "are they using the same device I am?" I'm not saying you aren't having an issue, but I would like to see this for myself. My 6S is super fast and responsive. No lag anywhere. And it restored from a backup.
Yeah it's nothing like unusable. Once the device is awake and running it's super-fast and runs like a dream. But it's pretty ugly seeing that unlock lag on such a new device.