My last question about The fall of the house of usher?

I just want to know some of you guys opinions because I just got done reading it. The story is presented from the point of view of a typical Poe narrator - a character who claims to provide an objective view, but whose rationality becomes suspect during the course of the tale. What evidence can you find that the narrator's state of mind may be approaching Roderick's? How does this uncertainty about the narrator's objectivity affect your response to the story's events?