My 1993 2120 came with a Curtis soft-side. I think it's great being able to remove side and rear curtains in the summer. You get sun protection and in the woods branches don't try to pry you out of the seat. In winter, I put in the rear and right side curtains, but leave the left (step) side off. Little snow gets in unless there's blizzard conditions. Visibility and access are excellent. The Curtis soft-side curtains are a pain, with multiple snaps and velcro, but I'm only changing them twice a year. A lift-off left door would be useful, and I might make one from plywood or light metal sometime.
May be the newer Curtises aren't as tough, but this one is quite heavy and doesn't rock and roll. Looks kind of goofy, with the forward-sloped front glass, but you can't tell when your in it.
Jim