The four of us enjoy it too. My wife and I are involved with another bisexual m/f couple so deeply trusting that it's like the four of us are married to each other. No, it's not all about sex as we share a lot of our daily lives and interests with each other individually and collectively. I'm sure it's not what many people would consider to be normal but it is to us as the four of us have so much in common with each other and have "clicked" from day one that we're just enjoying what we have together because life is too short without the ability to love. We're just lucky enough that the four of use each have three people to share our love with all the time.
I'll respond based just on the title. As some of you might be aware, I came to the realization of my bisexuality over this past summer. This moment of realization brought about an inner peace. Instead of fighting or rationalizing it I just went with it. And what I love about being bi is not just the obvious doubling my chances of getting a date like Woody Allen once quipped, but also a broader mindedness of what sexuality even is. I'm not necessarily saying gender is meaningless, but what tends to be prohibited in a heteronormative world enjoys some possibilities for use if you like to swing both ways.