I am reading other people posts!
I think model-instancing is very important. As an example the game anno1404. Without model-instancing this game would not been possible like it is, the developers said. There are big cities, big forests etc. In this game many objects are the same, special the vegetation but it looks good! First they tried without instancing and with just some hundred models the framerate was to much less. So they added model-instancing. And you all forgot the shadowsystem! with PSSM shadows every model is rendered 4 times or more. If people use model-instancing in the right way, the difference between with and without model-instancing is amazing!