When we ordered the Terry TT we spec'd all factory options including the dual-pane windows. The lack of condensation was a huge plus, and a side benefit we didn't expect was how much quieter the camper was, the dual-pane windows do a lot to keep out exterior noise.
We just camped in this new 5er last weekend, with temps 27* the first nite. Even with only single pane windows, we kept the day/nite shades down and that air layer in front of the window kept condensation from forming at all. What's interesting is that this 5er with single pane windows and 3 slides stayed warmer with less furnace runtime than the Terry TT that had dual pane windows and one slide. While those are factors for sure, the thicker walls and insulated/heated basement also help quite a bit.
Worth noting, if the tanks are new and aren't properly purged on the first fill, the air inside compresses and you only get about half as much propane in the tank as you should.