As one who often writes books from the point of view of the opposite gender, I'm particularly observant of criticism leveled at authors for using this device. Now in some cases, it's justified. If the story is attempting to tell a tale unique to a specific gender-related experience, then you're kind of setting yourself up for a gut punch. If not though, I believe the character should be based on the believability of their actions and voice regardless of the author's sex.
Often, I see reviews online that say such unintelligent things as obviously, the author has never been a 13 year old girl, because she would never do such and such a thing. Or even better, no teenage girl thinks like that. Really? None? Does being a member of a gender clue you in on what every other member of your tribe thinks? I know I certainly wouldn't presume to know what all boys think about. So let's refrain from such statements, please.
Just because a character's experience doesn't match your experience, doesn't make it invalid. If the character's motivations are flawed that's one thing. If their actions aren't justified or properly presented, that's something too. But if they are, then I don't see gender coming into play. There is no reason one can or cannot act a certain way simply because of their gender. Naturally some behavior is more likely, but unlikely behavior that is set up in the right manner is just as believable.
I have a suspicion that a lot of reviewers who write negatively about an author writing under a different gender are simply reacting to the seeing the author's name. Had the author's name not appeared, I surely doubt they would recognize the author as being other than the same gender of the main character. I don't think I'd see reviews online that read obviously this was written by a man.
I wonder why that is? I can only assume it comes from the perception of being threatened, that somehow your story is being corrupted. Whatever reason, it seems quite silly to me and not very enlightened.
Personally, I like to write from the point of view of opposite gender mostly because it forces me to find a unique voice for a character. My teenage boy characters tend to sound like me and think like me more often than not and writing in my own voice isn't nearly as interesting as writing in a voice that doesn't belong to me.