I didn't start drinking until I was 18, and I cut back a fair bit since I graduated last December.
I still don't have any problem tossing in a season of Seinfeld and draining a six-pack after work, or a bottle of wine with dinner, however. Compared to most people, I assume I'm a bit of a heavy drinker, but I'm OK with that.
I drink alone sometimes, too, and that really freaks certain people out. I don't see the big problem.
I also rarely, if ever, get hangovers of even the slightest potency. Nothing a couple scrambled eggs can't fix. Even the day after my 21st, on which I had 22 shots that I remember, I got up and worked an eight-hour shift. Just lucky, I guess.