Thanks, nameless and GAW. I agree with you both.
My point is that #5 alone is too hard to judge. Yes you can think that the other person is amazing (and you should) but that doesn’t prove that he/she is! It should, but it might not. Hopefully, GAW’s experience is the norm. But I bet that your feeling that she was amazing was not enough at the time. I bet you did some checking anyway.
My point about surprises was that there are elements of personality that are hidden. Whether or not they detract from your feeling that the other person is amazing is moot, because it is possible that it will detract. If it is possible, but never shows up during dating, then #5 is a worthless indicator.
I’m just trying to say that #5 cannot be eliminated (it is necessary) but at the same time, it is not enough to preclude #1-4 (or some other forms of checking that weren’t brought up).