We just returned from a two week trip through Colorado with a new Atwood "Edwin" replacement window in our Sunseeker 2300 entry door. So far, it's my favorite mod.
This window replaces the frosted glass provided by the factory. It doesn't have a screen, but what good is a screen on a door that already has a screened door? From the drivers seat, I can look back and see approaching traffic at intersections I couldn't see at all prior to the replacement. The added ventilation is a plus, and the improved view from the coach has provided enjoyment by easily seeing wildlife in the Tetons while eating breakfast at the dinette.
Installation took about 15 minutes including removal of the old window. You can read about it here... EDWIN Replacement Door Window