Bisexuals have many things in common with gay men and lesbians. At the same time there are some differences that can make our experience distinctive.
Bisexuals get flak from both sides; we can't take for granted the support of either the mainstream or the gay/lesbian communities.
As someone said (half joking): "Everybody thinks bisexuals are perverts".
There are few places where bisexuality is the norm.
If a bisexual leaves a relationship with one sex and enters a relationship with the other sex, they may risk loosing their friends and their support network, especially if they have not publicly identified as bisexual.
A socially experienced bisexual may have two public personas and be able to function in either community. This, in itself, is not unhealthy. However, carried to an extreme, this can become a "double closet" where one is hiding significant facts about oneself in both places. This can make it more difficult to develop an integrated self-image.
(This is a consequence of structural bias against bisexuals in society.)
Coming out as bisexual may be an incremental process of coming to terms with first one sort of sexual attraction then another, then trying to live with what society says are opposites.
Coming out as gay/lesbian is more clearly a process of directly opposing heterosexual socialization. In developing their sexual identity, bisexuals can't totally reject their heterosexual socialization in favor of homosexuality, instead they must pick, choose and synthesize.
Developing a bisexual identity can be more time consuming because of the complexity of the issues and the relative lack of social support.
It is more difficult to "come out" publicly as bisexual because people cannot in general infer your bisexuality from your relationships or other subtle signs. It's difficult to "prove" one is bisexual to everyone's satisfaction.
It has been suggested that bisexuals sometimes have to "come out" over and over because people seem to keep forgetting one "side" or the other of their sexuality.
I suspect that bisexuals are even more likely than gay men and lesbians to be impatient with the limitations of labels like "gay" or "straight". Bisexuals are in the middle of a social polarization. Heterosexism sets up an "either/or"; we tend to respond with "both/and" or sometimes "none of the above".
I suspect the grace or lack thereof that people have in exploring their sexuality has to do in part with the variety and flexibility of the models of sexuality presented to them in advance.
I had the benefit of meeting a few bisexuals early in my coming out process, so I was always aware of this alternative and didn't always experience a sharp gay/straight split. But, initially, I felt this was a rare and exceptional experience. It has taken me a long time to have islands of this sort of unified community in my life on an on-going basis.