There's not always a clear divide between original
research, and using the
subject as a primary source.
Exactly. That is the key point. In the pinball example, looking at the
game and playing it a little just to find out what how many points
different things are worth is probably ok (<ref>{{cite pinball
machine|title=Addams Family|manufacturer=|played=26/7/07}}</ref>)
playing lots of games in order to determine how difficult a game it is
would be OR. The dividing line is somewhere inbetween - I don't know
where.