Honestly people are really over exagerating. I live in Montreal and trust me it gets very cold. A few days days a year the temperature *can* drop to below -30 Celsius (0 Celsius is 32 farenheit to give you an idea) and I've had no issues with the heating system. Obviously at that temperature you are wearing boots to keep your feet warm. The only real issue if we could say so is that your mileage will suffer (25%-35% loss in range at a minimum). But at that temperature you just plan ahead and make sure to have more energy then required and also you pre heat the car while it's plugged in in the morning before leaving home. In my opinion the heating is much faster to get to the set temperature in my Tesla then it was with my Lexus. I don't suggest to use the range mode unless you really need extra range to get to your destination - range mode will automatically affect the heating system.
Thank you! Very helpful to know. If its good enough for Montreal it should be good enough for further south