One of the unexpected impacts I experienced when going to zero cups per-day was that I suddenly started dreaming more often and more vividly. It was like how I remember sleep as a child, with nights full of weird and wonderful dreams, rather than only remembering one or two dreams a week as an adult.

I only had this effect when going completely zero caffeine, not when I cut down to one cup a day.

Unfortunately coffee is a vicious cycle, where I end up picking the habit back up on work trips. Before I know it I'm drinking a cup of coffee while writing a reply on HN about how great it was when I gave it up.

Oh, interesting, and I can relate!

Incidentally, after being a heavy coffee drinker (5-10 cups per day for many years), I cut my coffee intake to zero. This happened around 3 years ago. At the same time, I started using earplugs every night. Pretty much since I started doing that, I dream several times a week. Previously I had dreams maybe once per month. I suspected that this dreaming was the effect of using earplugs, but now I wonder if it might be the caused by me not drinking coffee (for the curious, I replaced coffee with green tea).