I used it last year in October for my elk hunts here in Colorado at 10,000 feet. Heater worked great but I did have condensation issues. My roof vent is broken so I plan to replace that so I can leave it a little cracked.
The main issues I had was the sheets freezing to the canvas in the corners and when being close to a window while at the dinette my back would get cold being close to the window with nothing between me and the outside but glass.
I didn’t really have an issue staying warm in bed but I also had plenty of blankets.