Caffeine gets a lot of love and hate. Personally, I think it's close to a miracle molecule. What other drug can give such an effective boost to wakefulness, mood, and focus with the only main side effects being possible sleep loss and jitteriness/discomfort? Many focus on physical side effects, but I have never seen any evidence of it negatively affecting mental health, despite being psychoactive. I have not consumed amphetamine, cocaine, or the like, but I have tried many legal "nootropics" and all are <= effective compared caffeine with more side-effects.

I take a small portion of a caffeine tablet under my tongue for exercising and occasionally for study and work. I am more healthy today than I was a year or more ago, a large part in thanks to caffeine getting me off my butt to run when I don't feel like running, and (safely) allowing me to push myself harder and get a better cardiovascular workout.

Is it accurate to call it a vitamin-like nutrient? No, because obviously it's not like vitamin D3 or C where very high levels are beneficial and we don't need caffeine to survive, but it can be taken in moderate doses indefinitely and still positively impact one's health. It depends on how you define "nutrient".