I've been cutting my own hair since the 8th grade. I had a bad incident with some lady that cut my bangs too short the summer before I started high school (I explicitly said to cut them just below my eyebrows, not above), and refused to get anymore "professional" haircuts.
I've gotten pretty good at layering and trims, if I say so myself. :) I was good at trimming bangs too, but I've grown them out since, so that's not really relevant anymore. I've also given other people haircuts. Girls only though, I get nervous about cutting guy hair, because it seems like it requires more precision since guys usually cut it short.