One of the biggest things for me is discovering firsthand exactly why women do some of the things that they do. The light bulb comes on multiple times a day now.
Skin - softer now, but now dry all of the time. I get the needing to apply lotion all of the time.
I did not really suffer any PMS like symptoms until I started progesterone last month. I now understand a little better about what PMS is like.
Boobs!
I really crave salty foods now. I get why pregnant women want pickles and ice cream at 3am.
I now fully understand chocolate and why you want some. It is divine

My sense of smell has greatly improved, and i've discovered that the world is a really stinky place.
Strangely, my sense of taste has dulled. I can eat hotter/spicier food now and not break a sweat.
I am getting weaker by the day. I just went to Costco and getting the heavy stuff in and out of my car was a chore. Getting lids off? Forget about it. I also realized that I can't defend myself in a fight with another guy now.
I now get up very early each morning and I am generally excited and happy about each day. I used to be able to sleep for 10 hours or more at a stretch but these days I'm lucky to make 6. I have a far more positive outlook, and small things don't bother me as much (unless it's progesterone week then look out!). I can't stay up late anymore either; I'm generally in bed by nine.
I have no tolerance for alcohol. A glass of wine and I'm done. I used to be able to knock back a 12 pack of beer at one sitting.
My fears and worrying about anything and everything is no more; my being antisocial and acting like a hermit like days are gone, hopefully forever. I
want to get out and do new stuff now. My give-a-crap meter is broken too

I just don't care what other people think.
Weight has to be constantly monitored; the old carefree days of eating a burger or a steak are gone. I eat nothing now and I still gain weight. When I do eat I can't eat near as much as I used to, and i've had to learn that a small portion of food is just fine.
The biggest mental change for me at the moment is the social transition, which of course was partially helped along by HRT. I have no fear about jumping into social situations now; but it boggles my mind if I think too much about what I'm in the middle of. So i don't think about it and just do it