As I understood it, Mary is, in the thought experiment, supposed to be very nearly omniscient - she knows EVERY PHYSICAL FACT about color and human perception of color.
My question is whether she's allowed (before exiting the room) to wire her brain up to a machine that stimulates her neurons exactly as if there was a red thing in front of her.
Would you agree that if she were allowed to use such a machine, then she would know which response her brain in fact would have?
Yes, I do, but I think that turns it into an unhelpful question. If she already knows enough to stimulate her neurons to generate what it feels like "exactly as if there was a red thing in front of her", then of course she won't learn anything from seeing red. But knowing enough to do that raises the question of how she could know she's generating the right feeling, which just regresses to the original dilemma. It's like saying, "If Mary knows everything, does she know a subset of everything?"
I thought the point of the scenario was to...
http://esr.ibiblio.org/?p=1192#more-1192
ADDED: Even if you disagree with ESR's take, and many will, this is the clearest definition I have seen on what qualia is. So it should present a useful starting point, even for those who strongly disagree, to argue from.