I use my watch every day and the GPS gets used at least three times a week. Regarding the barometric sensor, that is a good question. I do not know. I will have to do some googling around.
I did find something out that was interesting the other night though. I also run with a running dynamics pod to capture running dynamics. Sometimes the watch recognizes the pod right away and sometimes not. Anyway. Last night the running pod was recognized at the start of the run. And wouldn't you know it? There was no sudden jump in elevation. I am starting to wonder if the running dynamics pod, which captures ground contact time, is having some sort of impact on the elevation profile readings. I will do some more experimenting with the running pod to see it the pod is having any impact.