This is an excellent thread Nero, I hope it gets a lot of responses. I'd be interested in reading them all.
I'm only partially through transitioning. But I can already say my outlook is much more positive. I cut my hair, got a binder, passed, and all of a sudden it seemed like 40% of my social phobia disappeared. I've discovered I actually don't hate people. I just hated how they acted towards me, and I hated the painful awareness of being female when around them. I hated that I couldn't so much as walk next to someone without wincing at how it felt to walk, at my moobs bouncing. So I was a recluse before, an antisocial hermit. I was sure I was going to go through my life totally alone. I was pretty sure I wouldn't live long past 20, and I didn't want to live much longer. Now? I'm still a huge introvert, but with a binder and some confidence born of people actually acknowledging me as male, I can cope with people. I don't walk into a room full of people, have them call my name, and feel like hitting someone or running away. I'm so much more optimistic. I still have clinical depression that can get really bad, but even with that I see myself living happily into my 70s, and I can imagine some future.
On stealth - I used to want to hide being biologically female from everyone. When I was young and imagining it, I was in another country and nobody knew. I wanted to forget all memories of puberty and pretend I never was a girl. Now, I've spent time learning about the trans community, reading about hate crimes, coming out to people and explaining things to them. If I could give up status of stealth in order to significantly help the community and make a difference in how people perceive transsexuals and gender in general, I would. I'm still trying to decide how, and to what extent I'm willing to reveal my past. And right now I just want the experience of stealth. But in the future it doesn't have to be necessary.
Surgery - I've always wanted top surgery. Nothing's changed there. Bottom surgery is something I never thought about before, but in sexual situations I've found some discomfort with my anatomy that I hadn't experienced before, and if the technology improves I'll consider it.
Sexuality - From puberty to the age of 13, I think I was mostly attracted to men. Then I was attracted to women, saw the lesbian community, saw that butch women were accepted, and decided I could be a lesbian. I have gone through periods of being primarily straight, but transitioning I find I'm equally comfortable with the idea of a gay relationship now. On T I expect I may even prefer one, since part of my hesitation before has been that I automatically compare myself physically to men, and when my body is so female I would feel ugly, even inferior next to a man with a fully male body. Having an ftm boyfriend has been a good compromise - I still see him fully as male and can connect emotionally to him in a way that with women is harder for me, and though he is physically much less feminine than me, I know he's facing the same kind of insecurities about his appearance. So I don't feel as threatened - that's probably some reflexive caveman instinct, now that I think about it.
With my life, I touched on it before. Until I decided to transition, or maybe later on when I was partially transitioned, I tried to think of my future as a woman and saw myself alone in an apartment after vet school with a cat. Then in the office, probably doing a brilliant job intellectually, but no interactions with coworkers. Those were the only images I could conjure. No friends, no family, no partner, no joys. I knew perfectly well I couldn't be in a relationship as a woman, and I was so depressed and cynical I foresaw myself cutting off all ties so I wouldn't have to deal with the panic in social situations. I could never function socially as a woman, so I actually reached a point where I tried to decide how I would methodically isolate myself while still maintaining income for survival. As I mentioned in my introductory post, I had no idea I could transition until last year, so this was me for about 5 years - I was suicidal when I was 12 and it didn't get much better from then on. I am entirely astonished I avoided killing myself. And now, I'm in a relationship partially due to being honest about who I am. I have too many ideas for careers and my future life to know what to do with, this is all a new world to me. I'd never thought about kids, marriage, who I would befriend, and now all of these possibilities are flooding me. I've switched from pessimist to optimist. Most importantly, I can imagine myself, the person I see in a mirror, as being in the future and connected to the world. So for me, transition has changed my life more than just my outlook. And as I'm sure has been the case for others before, I think it literally saved my life.