Hi mate, we met two other bikers that has also been down here last year in winter. A Japanese guy on his Africa Twin (Tetsu) and an Australian on his 1200GS (Peter) Both are also on this HUBB.
We left after only two nights, as the weather forecast was snow. Everything on the side of the road was snow and ice, so we could only stay on the road with the bike. The big dissapointment was the fact that we could not drive into the National Park, as the road was not graded down to the gravel and it had a thick layer of ice on it. I tried, but after only 200m realised this is a suicide mission and turned (very slowly) around. So we dont have the nice photo that most other travelers have of the end of the road sign. Camping were also out of the question, and we had to pay the expensive rates (Pesos 120 for double) at the hostal.
The road over the mountain pass just north of Ushuaia was tricky, especially the part that stays in the shadow. There were ice in many sections. We made it without falling over, so it is doable, but would be better in summer, you made the right choice to come later.
We got to do a ride with the sled-dogs, something we would not have been able to do if we were down here in summer, so there are pros and cons I guess.
Temprature was cold, between -3 degC (today) and 3, no rain though.
We are heading north now on Ruta 3.
PS: I have one or two photos on our website, "JC's RTW Adventure
. Just click on the Argentina section from the list on the left of the opening page. This will give you an idea what it looked like four days ago.