We had one on our GTX18 that was my grandfathers. Then my father retro-fitted a full steel cozy cab to it and we sold the soft door steel cab (for much less than the linked one). Shortly there after, my brother bought a GTX20 and was given the cozy cab. Wish we still had the original cab that was on the GTX18.
The soft cab isn't nearly as warm as the cozy cab. I also like the suicide door better on the soft cab than the regular hinged coz cab doors. I won't use the GTX18 much in the winter as I have a cozy cab on my Bolens 1250. But if one came up a decent price, I'd be interested.