The camera does not lag behind and neither do I have a low FPS. However let''s say when my simulation is running at 50fps and then suddenly slows down or increases then there occurs a lot of jerky movement, the kind of effect you get when the computer starts to suddenly read something from the hardisk when playing a game.
This does happen when I am using either directx9 or 8 but mysteriously this does not happen with OpenGL.