Mid-2010, and I'm still learning it, lol
Baseball is over. My softball league is over. I am now officially depressed...
I first got into sabermetrics after reading Bill James Abstracts in the 1980s when I was in college. I'm a math guy, so it was fascinating and easy for me to accept. As far as rejecting the traditional stats, I never totally rejected them. I never tell anyone that stats like BA and RBI are useless. They really aren't useless. It's just that the advanced stats tell us more about players in most cases.