I visited Ushuaia in July/August about five years ago. It was definitely cold, but that wasn't an issue to me. I like the cold and it was nice to see the mountains covered with snow.

The town is a bit rough and tumble, as can be expected. It felt like a Yukon mining village or something - kinda interesting. There was no shortage people - many were down for skiing or something.

One thing that is not to be missed is a boat trip through the Beagle Channel.

Don't let the naysayers dissuade you from visiting in the winter if you don't mind the cold.

I just got back from a trip to Angkor Wat where it was in the 90's (degrees and humidity). I would have gladly traded that for winter in Ushuaia!