which begs the question "What does a normal user who is signed-in actually see?"
I bet it's nothing like my results.
Normal users will see what the adwords preview tool shows, for most keywords that they search just once or twice.
But you raise a good question. What is the difference between personalised signed in search and personalised signed out search? From what I can signed out search resets itself every algo change but signed in search continues to remember your history.