Well, we've braved the first month of cold weather. Not entirely all sub-freezing, but we've had 5-6 days in a row where the temps don't get above 32F.
We're running a 1500 watt heater in the basement continuously. That's worked down into the lower single digit temps we've had at night.
HOWEVER... lessons learned:
1) our black tank is positioned such that I just can't get much heat to it. So now we are putting about 10% Glycol windshield washer fluid in it (the blue stuff). Why that over the pink RV anti-freeze? Well, it's still rated to -20F (instead of -50F) but it's less than half the cost, and quantity is better than quality, it seems. In other words, better to have 6 gallons of blue fluid than 3 gallons of pink... it seems to mix better. (of course, the blue stuff is NOT safe for consumption. We strictly pour it down the toilet).
2) the icemaker line to the fridge had a plastic fitting that cracked (being exposed to the cold, I assume it had water that froze. I've capped it off at the metal line portion.
3) No matter how well you think you've drained your sewer line... you still need to pack it away or somehow it freezes into a giant black log.
4) we're not running city water. Just filling the fresh tank every few days.
5) in the living area it's taking 4500 watts worth of electric heaters to keep it warm... and when the temps drop to single digits we are having to run the propane furnace for 10-15 minutes in the morning before either of us is willing to brave the shower
Aside from that, things have been okay. Some days with high wind we're been forced to keep the slides in, but that's not the end of the world.