1. The Pixel camera app works, including all modes and settings. A camera that takes good photos was absolutely a requirement for me, and the FOSS camera apps are not quite as good yet.
2. I don't have Google Photos and the pixel camera app tries to launch google photos when you want to review the picture you just took. But there is a FOSS app called GPhotosShim that uses the same namespace as google photos and thus fools the camera into launching that app instead. Once launched, it just launches whatever media management app you actually have configured, so it's seamless.
3. Android Auto works!
4. Android QuickShare works!
5. NFC tags / Yubikey integration works!
6. Screencasting works!
7. Sensor access and internet access can be disabled for apps by default (and I do).