Thanks Gunter.
I suppose extra effort is required to use simplified reps, specifically of assemblies, to have significant overhead savings. With part models, simplified reps would have to be fully loaded anyway since you are "suppressing" features; but in assemblies, I could see a significant saving of resources if only the parts in the representation are loaded (and maybe the parts used for constraints).
From a user perspective, you get the option to show a simplified rep when placing the view if one exists. Actually it asks if you want to use a Combined State... making this less user friendly. I don't use these often so I wonder if the answer to the user interface is more a question of usability of view manager dialog.