Well derp... Oculus software version 13 kills Link compatibility.
So apparently don't run the PTC Beta versions (turn off the beta option). This creates a mismatch between the oculus software and quest firmware.
I had another play... some observations
- FOV feels bigger
- images don't feel as sharp, possibly FOV related
- Quest MIC sucks, very low pickup - this is a known issue
- actually feels a bit smoother than the CV1 in tracking and head movement
- Audio is a bit meh due to the speakers in the Quest, if you cup your hands over them it's sounds good so it's a design issue for the type of game I suspect