I think part of the problem is that the display range is different for objects in the center and at the edge of the screen. Objects and fog are drawn farther away when they're at the edge of the screen.
To see this, fly high enough that the trees are a sort of moving square that follows you around, and then look out the side over the wing. You should see a line on the ground where the trees stop getting drawn. Then kick rudder back and forth. You'll see the line of trees move in and out, being drawn farther away as they are at the left and right edges of the screen, and being drawn closer in at the center of the screen.
It's like the object and fog draw range isn't a circle around the plane, rather it's a square, rectangle, or oval that rotates based on plane heading. This may be causing the jagged horizons people are seeing, and it also looks really bad and inconsistent when turning or maneuvering. Making it a circle or at least not as obviously uneven might look a lot better.
