Among my friends, peers, and coworkers (generally 22-40), I've noticed many women calling mixed groups - and even groups of women - "guys". In the same groups, in casual parlance, women will call other women "dude".
I think these terms are losing their gender-specificity and merely becoming a way to refer to a generic (non-sex/gender specified) person.
Of course, depending on your peer groups, and the level of formality in communication, your situation may be different. (i.e. if your entire peer-group is hypersensitive, politically-correct language police, feel free to modify.)
I know a number of women who call mixed groups and even groups of women "guys", and I know women who don't like to be called "guy". I don't think the existence of the first group justifies in any way me being an asshole to the second group. I think it's reasonable to be accomodating here, especially as someone who just dropped into someone's irc channel.
I think these terms are losing their gender-specificity and merely becoming a way to refer to a generic (non-sex/gender specified) person.
Of course, depending on your peer groups, and the level of formality in communication, your situation may be different. (i.e. if your entire peer-group is hypersensitive, politically-correct language police, feel free to modify.)