Reactions have so far been mixed. I began to wonder: is gender such an important, indeed essential part of a god or goddess? Let us try some thought experiments. The goddess Aphrodite, for example, is the goddess of generation, passionate love, the sea. She is invoked in those aspects. Lucretius (who doesn't believe in her) calls upon her at the beginning of his De Rerum Natura as the "alma" - nourishing - mother. It is important that she is a mother, as the things that flow from that are feminine. If you replaced it with Pater Aphroditus, you would have an entirely different set of affairs.
Some gods are resolutely tied up with gender. Juno is the goddess of child-birth, for example; it would seem contrary to endow a male god with her attributes. Others are ambiguous. Dionysus is a god who has long hair like a woman, and who hangs around with women. He is a feminine man: not, importantly, a masculine woman. Artemis, though very definitely feminine, does things that are largely considered male - hunting; she would not be the same if she were a man who did things considered to be feminine. Athena has the attributes of a warrior, and of wisdom. Compare her to Ares - he is just war, pure and simple
Thor is an elemental god, a god of thunder and lightning, and a smith god. He has aspects of Zeus and of Hephaestus; Tacitus thought of him as Hercules. What happens if you switch genders with these gods and all the stories that are told about them? The scene in the Iliad, where Thetis supplicates Zeus, works because Thetis is a mother concerned about her son; switch Zeus into a mother too, and the dynamic shifts. Thor as woman suddenly has a whole new set of attributes, relationships with her wives, her brothers, her father Odin.
There is a lot to be said for playing with mythology. It is there to be tinkered with, there to be recast in different forms, and to have variegated lights thrown on it. That is why it is still alive, and why it still speaks to us, and why we always return to it. There is no reason why Marvel should not introduce a female aspect of Thor. But to say that Thor is a woman is to displace something fundamental about myth and its sources: in fact to disregard them entirely, for the sake of a marketing exercise. The power of myth lies in certain unchanging elements: to change those is to deflate it entirely.
