This is not very scientific, of course, but I am interested to see if using True Tone seems to affect battery life in a substantial way. Please only vote if you have an iPhone X.
6-7 hours, True Tone off. To be fair though, I have been using a higher brightness than I usually use because of the natural way the OLED looks for me in dark conditions. I'd say round 80-85% compared to 70% on past iPhones.