On my 4th Pixel XL now..
1st: (pre-ordered day 1) Boot loop right out of the box -- adb sideloaded latest OTA, same issue. Never booted to OS.
2nd: Worked great for a few weeks, then, while using it lying in bed, a white stripe about 1/8" wide popped up on the right 1/3rd of the screen. Present in bootloader and not in a screenshot taken on the device, so definitely HW defect.
3rd: Screen flicker noted in this thread
4th: Arrived yesterday, didn't even fool with setting it up before charging and testing -- screen flicker..

I'm on hold w/ Pixel support now. I'm inclined to keep my 3rd one, and get another replacement in a few months.
LK