I spent a few years completely avoiding caffeine and the last few years consuming a lot of caffeine (via coffee). For me, in terms of alertness or productivity, there is a difference only in the "transition" period when the body is readjusting to the (lack of) caffeine. Otherwise the only difference is that by being used to caffeine, I can enjoy making and drinking good coffee (one of the simple pleasures of life).
This is what it is for me. I've quit coffee and caffeine multiple times, sometimes for a year usually just for a month or two. Just to see if I enjoy life more without it. But I just simply love the routine of coffee in the morning. Also I've found nothing that compares to the flavor of black coffee. I only drink coffee in the morning, but several cups (french press). One of the simple pleasures in life for me as well.
