I had to think about it, but here goes. I've been aware of OBP since I was a kid too. When I played organized baseball in fact, I kept track of my own OBP. Let me hasten to add, a big part of the reason I did was that I was not a good hitter. In pickup games I could hit the ball as good as anybody, but any pitcher who was actually trying to get me out with fastballs and curves could get me out easy enough.
As far as really analyzing baseball stats like we do now though, I didn't get into that until about 10 years ago-thanks to the internet.
OBP is not the end-all and be-all by any means, no. I like the point that elktonnick raised about Bill James saying that the big factor is the leadoff man getting on base.
Baseball is not as complicated a game as we sometimes make it with the stats. All that really matters is who wins the games, who makes the playoffs, who wins it all. All this analysis and debate is mostly for amusement purposes. Obviously I'm one of the people who enjoys it.