I'm a woman living in the UK. The word 'cunt' is normally used to describe men - or people in general - rather than women, and I certainly don't hear it as sexist at all when used in this manner. 'Cunt' is not normally used to describe a woman - at least I've never heard it used this way. If you want to insult a woman in the UK, 'bitch' or 'cow' are the gender-specific words to use. Hope that clears it up for you.
I wish I could say that was the case, but in my manor - currently Bermondsey - cf 'Nil By Mouth', the film - that the epithet is used pretty much all the time, throughout sexes, unless it's a younger man, in which case they are called 'boy', a word which I personally have bigger problems with than 'cunt'.
I would agree with both Ripley and Stelfox about usages - to approach the word from a feminist perspective is entirely correct, and it's perpetually shocking within this forum to see a lack of feminist ideology - i.e literally people who haven't read shit and don't know what they're fucking talking about - chatting, but I also agree with Stel that it's an amazing word to say, assonance wise. Vim also correctly pointed out that it's also used as a term of affection, there seem to be three uses - admiration, affection, and abuse.
I spoke to a friend about this, and in Glasgow, from what the friend has said, that he has never heard the word referred to as a synonym for vagina, which is interesting. To the extent that at 15 they thought that the word meant 'bastard' only worse.
Like I said that's fascinating for me cos it's used every three words round our way.