One big thing I saw drop was my anxiety. Anxiety has been passed down by my father, and while it's somewhat mild in me, my dad & sister would be having panic attacks at my age. For me, I never went into a straight panic but it can be hard for me to feel safe. I'm a very hard worker with a lot of responsibility, so of course the anxiety has plenty to feed upon ("This isn't done, gotta do this, gotta do that."). Coffee would fuel that kind of behavior as if it were some kind of battle and take it all on. Then when the inevitable crash came, I would have to be looking to supplement it.
Like I said, I'm only a week in but what the OP says about waking up is very true and probably my favorite aspect of quitting coffee. I'll wake up at 6:30 and wanna just get up. When 11 or 12 rolls around, I fall asleep very naturally and wouldn't be able to stay awake even if I wanted to. It's worth a shot for everyone. Unlike the OP, I went completely cold turkey on the caffeine I should mention.