Many people say that gendered language is especially important in Japanese. To a point, I can understand this, but only to a certain distance. For example, if I (Fe/male) were to say 'Wow, that show was impressive!', in a neutral pitch, it wouldn't sound queer if I were male of female. However, if I were to say 'Ooh, that show was fantastic!' (generally female sounding), or 'Damn, that show was fucking awesome, man.' (generally male sounding), it wouldn't be wrong, but to some it would sound quite strange.
I can understand this in Japanese too, but some stress it to a point I can't believe. For instance, for the most part, things in Japanese seen as 'masculine' (most common examples I've heard), are: 僕、俺、だ（copula）、か（interrogative）; and ones seen as 'feminine' are: 私、あたし、です、〜ます、の （interrogative）、わ. Now, keep in mind, 私、です、〜ます、only apply in casual conversations and situations, and in polite ones, it is 'correct', and wouldn't be 'feminine'. Similarly, の as an interrogative, I hear isn't feminine in some situations as well, and わ is sometimes used by males, and in some dialects, it's not feminine at all. (correct me if I'm wrong).
Also, things seen as masculine, I hear females saying all the time, and at no sacrifice to their femininity. Although I have yet to hear a woman say 俺, there has been no shortage to the amount of women saying 僕、だ、か. Although more women are using 'masculine' language than men using 'feminine' language, it is still there.
I have heard that if you don't use the appropriate set, people will be confused, maybe upset. If you mix them, you may be seen as a transvestite or a hermaphrodite. Is this really true? Just how important is gendered language in Japanese?