I've been on T for about 5 months now. The first thing I noticed was darkening and increase in the hairs around my bellybutton. Then it was the hair on my stomach. It's still thin, but it's darker and goes in towards the middle. Then it was some chest hair. There's not a lot but it's definitely noticeable. The whole time the hair on my arms and legs has been getting darker and thickening. I had blonde hair most places (except my pits and special area), but the new hair is all darker. It's funny because my arm hair was slowly increasing in towards my inner arm, and the top of my hand. But the hair that was there before is still blonde. So I have a racing stripe along my arm. I am also getting hair in places you wouldn't think (the inside of my elbow, the top of my feet, my inner thighs). There was no hair on my knees before, but now there is. The hair on my toes and knuckles is much more noticeable now. The hair on the back of my hands is the hair related changes I am noticing most often.
As for facial hair, I am not entirely sure yet. I have been shaving it since I started T due to fears of the dreaded dirty teenage mustache. I let it grow last week, though, and it's still really light and only noticeable close up, but it sure feels like facial hair. It's the area of my chin, neck, and a bit up my cheek. Also there is definitely upper lip hair, and it's pretty visible. I have a few longer hairs around the sideburn area, but you wouldn't notice unless you were looking for them. As for the chin hair, though, there's lots of it, but the hairs themselves are still quite thin and light coloured.
I haven't noticed a change in armpit hair since I tend to shave it occasionally. But my hair line (forehead) is definitely changing. It's more square now, and I like it. The parts around the temples receded a bit to form "corners".
