It's been mentioned before in this thread, but I think it's worth repeating. I think a lot of people think that the only way to send a large company like Marvel (or any other company in the entertainment industry) a message is to vote with your wallet. If a comic book company pulls such a silly stunt like turning Thor into a woman, it's best to show your disapproval by not buying those comics. If you buy a comic to see if it's really that bad and you end up disappointed, it's no skin off Marvel's nose because they already have your money.

Of course, reviews are a good way to figure out whether comic books are good or bad, but in my experience it's rare to find reviews that do not spoil a large portion of the plot.