My boyfriend and I talk about this all the time. We don't share the same taste in women, but there are a few we agree on - the same with men. The difference between us is that while I don't think he'd ever actually 'do the thing', like BeMy had referenced to in her post, I probably would just because I'm sexually attracted to both men and women. While I'm obviously more attracted to men, my boyfriend knows that I'm not joking when I say, for example, that I'd 'tear Christina Hendricks apart'. xD I would. And she'd love it.
Sexual attraction is healthy, regardless of which gender you're looking at. If you're comfortable enough in your sexuality to appreciate your own sex, I think you're doing pretty well. You don't have to necessarily be down to sleep with the person, but I think same-sex hall passes are 150% wonderful and healthy - especially if you and your partner are comfortable enough with each other to say that kind of shit and not have the other be judgy about it.