As a long standing Las Vegas local, we have seen it all. We went to the High Roller, excited to see the newest attraction. I have a fear of heights, but I felt I would be safe on the High Roller.
The pods are in continual motion, but very slow. You do not feel the height. I would be more concerned with someone who doesn't like closed spaces vs heights in the pod.
The sound echos off the walls pretty easy so the person across the pod can be speaking to the person next to them and it feels they are sitting right next to you.
We went during the day and plan to go back at night, so we have both experiences.
I would recommend someone contacting the Linq or other hotels to clean up their roofs as this is part of the view. Some pretty bad looking views out there.