Every time a new doctor regenerates, people are crying out loud, that the only real doctor was [insert your favorite doctor here], and the new one could not possibly replace the old one. And guess what: They were never supposed to!

Nonetheless it is nothing new, that people are shouting now. However it is a shame, that they are focusing on gender instead of the usual stuff. Missy set the precedence that regenerations are not bound to the same gender, so to all you "the doctor is a man"-guys: Get over it and give her the same chance, as you gave all the others before her! I don't know her, but as far as I know, she is supposed to be a good actress.

I think, a woman may bring a whole lot of new possibilities to the character. Just think about the scene(s), when the doctor discovers him-/herself, that she is a woman now. He might have gotten used to being a man just as much as the audience has. He knows intellectually, that it could happen, but discovering for herself that it happened is something entirely different and I expect a lot of fun to watch.

@sandrosaurus: It is not really a cross over episode, but at least the crossover starts here. Although you don't miss a thing of the crossover, when you start with "The Flash". Loved the crossover!

I love the crossovers! And this one is exceptionally great.
I found the episode labeled as Invasion!(2), which was a bit odd at first. Were is number one, because Arrows part is (3)? So I guess (HOPE), the one from Legends of Tomorrow will be the labeled "Invasion!(1)", which is the crossing of the t and the dot on the i for this cross over. I did not see the first/last one, but since Legends of Tomorrow is about time travelling this makes sense to me and I would LOVE this little twist in numbering so much!