The most immediate and significant changes are the mental ones. They might not actually be due to the hormones, themselves, but rather as a subconscious celebration of moving forward; however, these changes are nonetheless very real. You tend to be happier, more energetic, less depressed (if that was an issue), and more motivated in general... at least in my experience.
After a couple to a few months, you will notice breast growth. This continues for years, as it does for cis females in puberty, however the changes in this area can potentially be quite significant in the first year. Personally, I have experienced very little breast growth after a year and a half... but that is probably just because I'm underweight.
Apparently, estrogen makes weight gain easier. I haven't noticed this, myself, but I have known friends that have.
Subtle changes to the fat tissue in the face are the target effect most people have... and they are very real. Even being underweight, I have noticed very significant changes to my face that have taken me from a feminine guy to a feminine girl in terms of physical appearance. Bone structure does not change, unfortunately. These changes are first noticeable from a few months to a year.
Body hair is reduced, generally. I've noticed that most of my hair is lessened, and thinner/finer... some people have reported losing a lot of body hair, but I have not seen that myself. This takes a longer period of time... from a few months to a couple years to notice.
I noticed that my facial hair grew at a slower rate, even before laser. This was almost immediate for me.
And that's about all I can think of.
I'm a little weaker, but I was weak before anyway... not a huge difference, and I should definitely work out. Best of luck, Lost.
