I personally disagree with the choice - the Doctor is not a woman.
It will be interesting to see how the Doctor's personality changes with a "feminine" persona.
Will she be as rude and as overbearing as the Doctor quite often was?
Or will her character be "softened" and "feminized."
Actually, the more I think about it, the more I think that it will be interesting to see how the writers deal with the character.
Even today, strong women are treated differently than strong men.
Strong men are mavericks, strong women bitches.
Men have a commanding presence and get things done, women are naggers, etc.
If looking back at 50 years of the Doctor, if a woman had been playing the role at any time, would the men he had been "bullying" if you like have put up with that from a woman?
Well...I guess we'll see.