So my approx 12 hours of use thoughts...
Definitely feels more responsive than the Pixel 3 XL, I haven't experienced any sort of lag so far. I like the extra settings that Oxygen OS provides, they actually useful unlike some of the stuff Samsung thinks you need on your phone.
It's much nicer to hold than the P3XL. The shape of the phone just feels more comfortable and it's slightly lighter in weight.
I took a few comparison pictures outside last night around 10pm and liked the 6T pictures more than the P3XL, which I did not expect.
Things I might miss from the P3/XL: Call screening, I've been getting an asinine amount of spam calls lately and it looks like that is not available on the 6T. Same for the visual voice mail. Being on Google Fi that is one thing that I lose. I don't get a ton of non-spam calls anyway but VVM is nice to have. Disregard, I just left myself a voice mail and the 6T does have it's own version of VVM that works.
Questions:
1. Can you disable the "App is using location" notification? It's part of Google Play Services and you can turn off all notifications for that, but I'd rather not go that route. It does wake the screen every time something calls up my location. Found a solution on reddit.
2. Do you keep the factory installed screen protector on or remove it? I generally do not use screen protectors and am on the fence about this one. It adds a little tackyness (as in sticky, not ugly) to swiping but I think helps with typing. It also seems to get some static cling. As a pet owner that means I'm constantly wiping fur off the screen, something I haven't really experienced on other phones.
TL;DR: I really like it, need to give it a few more days of use to decide whether to keep the 6T or the P3XL.