When I was between 17 and 27, most of the girls I dated were bi-sexual. I even ad-libbed a Morrissey style joke song called "All my exes are bi-sexual" at band practice one night.
After the first one, the fact that they were bi-sexual didn't have an impact on my attraction. Being young, my first thoughts about dating a bi-sexual girl were:Hey, my chances of being in a male-female-female threesome just went up exponentially.
There were a couple of times that I felt like I was being trapped. She would talk about girls she found attractive, or movie stars, or whatever. It was strange to be watching a movie and thinking "In a perfect world, I would so do _actress name here_" only to have my date tell me just about the same thing. Having dated a girl who would actually bait me into complimenting her only to use what I said as an excuse for an argument (cognitive dissonance at work. She thought she was crap, so if I said she wasn't, I must have been lying...and then the fight started), I wasn't sure if she was just sharing because she felt comfortable enough with me, or if she was waiting for me to say the same thing and launch into a chorus of "so, I'm not enough for you?"
I also used to wear my hair long, being in a band thing and all that - but even before. I noticed that most of the bi-girls I dated told me that my hair was one of the first things they noticed/were attracted to. My longest term bi-sexual girlfriend was completely against me having any type of facial hair. As strange as it might sound, it was almost like her interest in me waned the more "traditionally masculine" I appeared.