"The capacitive buttons alone caused me prefer using the OnePlus to just about any other Android I’ve used this year. Manufacturers removed these in a spasm of penny-pitching a couple of years ago, but they make it vastly easier to operate the phone in the car, I find. Curiously these never light up"
Unless things have changed for the 3T, there is a setting to have them light up, but annoyingly they only light up when you have used one. I'd much prefer that they were on whenever the screen is on. And agreed about car use, the fingerprint reader as a physical home button makes life much easier and less distracting.
As an aside, apparently the back camera now uses a sapphire instead of whatever is in the standard 3.
I'm glad I got my 3 when I did as I don't need the extra features and wouldn't have spent that the extra for a 3T.
Edit: I've just noticed that you included a screenshot of the Buttons settings page and it shows the the Backlight option for the capacitive keys.