So, here's my experience: there's really two parts to my GID. There's the social aspect and the biological aspect. I hate being treated like a man. It's so not me. I like certain things that have historically been treated as a male activity, such as playing video games or reading comic books or what have you. But I hated when someone would be like, "You're the man - fix the car." Or "You're a man - get out of the kitchen." Or "you're a man - you'd never understand this woman's problem." Or "You're a man - you only want sex." Or such gender sterotypical bull->-bleeped-<- like that. I found it insulting and I felt inadequate, because I couldn't show the other person that I really wasn't a man. I like being approached as a woman, especially by other women. Partly because I'm a lesbian and I love having a partner relate to me as a woman. As for friends, I love being part of the "girl's club." That's where I've felt like I've belonged for so long - I have very few guy friends since I have such trouble relating to them. Girls make way more sense to me.
The biological part was everything that I didn't like about my body. Which was mostly whatever testosterone did to it - the secondary sex characteristics. Funny that those tend to be the gender queues to others on how to interact with a person. Maybe they're both tied in together in my psyche. It's those that I've wanted to change so that I'm comfortable with my own body.
I believe that prior to hormone therapy, you can experience being treated as a woman, but you cannot experience what it feels like to biologically feel like a woman. I had an idea of what psychological/emotional changes to expect from HT, but actually feeling it is a different (though similar) story. We are all unique individuals. And when one transgirl says she became more emotional, that "more emotional" state for her could be an average day for another person who is biologically male. It's all relative, and with that being the case, I think the ultimate litmus test on whether you will enjoy being female or not is hormone therapy and presenting in social situations as a woman. If it works for you, then it's for you. If it doesn't, then it doesn't. It doesn't get much clear cut than that.