I do like the cab, it's a whole lot better than being out in the wind, like I was for the last 18 years... It's a Curtis. I am putting a heater in it right now.
I bought the tractor this past March and only used it for one storm. While the velcro attachment of the vinyl sides was in bad shape, even still it kept out most of the snow and wind. I am redoing that now as well, so between that and the heater I expect it to be fairly comfortable in there this year.
That said, I do have a complaint about the Curtis. It's ridiculously expensive for what you get. I considered buying a new tractor and I was quoted over $4000 for just the cab, not including the heater. And that is for the soft-sided one like I have - some kind of plastic-cloth around the cowl, flexible vinyl on the sides/back, and even the doors, while they have rigid frames and are well built, have a flexible vinyl as the "window". Just the heater was $400, parts only - I'm installing it.