The major problem that I have found with the Depth Queing is that if there are objects close to the camera's plane, or behind the camera's plane, the automatic scaling factors screw up and you get pretty poor results.

This can especially become a problem in animations if you are attempting to rotate the camera or move it through the scene.

I have recently emailed Curious' tech support and wish list with a report of this and a suggestion that the automatic scaling should be abandoned and the user is given the ability to define the scaling or blending factors explicitly on the render menu, or as dial parameters on the universe object, if there are any future releases planned ;-)

BTW: if you enable Depth Cueing, turn off all the lights, set the background colour to white and zero all ambience you can effectively render depth map images which are useful for Depth of Field effects and other post processing, so long as you can avoid the bugs.