cosmicolor: Curing a phobia is something that tends to happen gradually, slowly. I would be suprised if Floor 3 was an instant cure for arachnophobia. It might help some people but not others, and I know that sudden exposure to a phobia might well make things worse. It's stressful, too, and video games are meant to be entertainment, not stressful experiences.
Plus, I have seen people on other boards say that they haven't brought this excellent game because of said spiders, so I think it would do nothing but good for the developers to include something like the "spider slider" that they made a concept of, or for an eventual no-spiders mod to appear.
of course it takes time, but it's a fact that watching an animated spider in a videogame is much less stressful than getting a real spider thrown in your face :D so it is a good start to cure yourself...
as I said above, I am arachnophobic, but even though the mere sound of those little legs tapping behind the wall gives me creeps and I really got scared once when the spider surprised me from behind the corner, these spiders really aren't that bad.
I'd say if you actually see the spider from this game attacking you and it prevents you from playing the game because of your phobia, you should really get some professional help to get rid of the phobia. it's serious.