Y'know, I also feared androgen insensitivity at first...
About how long it takes for changes... *thinks* I believe the first thing I really noticed was my voice. After about a week I noticed I couldn't make sounds as high as I could before. Before starting T, I did a couple voice recordings of me humming my entire range from low to high. After a week, I couldn't do the highest sounds; my voice just stopped and nothing came out. My throat was also tight--not sore per se, but just... tense. After a few more weeks, I noticed I was able to hum deeper than before T. But these small changes were only something I'd notice because they happened at the extreme ends of my voice. It took 7 weeks for other people to notice a definite change in my speaking voice. It took 14 weeks to be 'sirred' on the phone.
As for libido, I really did not experience much of an increase at all. I was expecting something so intense and powerful that I would want to jack off several times a day (like when I went through puberty the first time

). But that didn't happen; my libido has pretty much stayed the same, though it has always been fairly high (how does one measure such a thing, anyways?). I will say that the little guy did grow a surprising amount in only a week, though (to a bit less than 1/4" in diameter; no real change in length).
Apart from that, the first week (heck, the first few weeks) was pretty uneventful. I noticed more energy in the first week, too, but that could've just been psychological. I started on the "standard" dose right away, just for reference.