If I drink enough (2-3 good strong cups in the space of a day) I will get pretty hot and flushed, typical stimulant effects, really. Caffeine has a very insidious grip on people's lifestyles, I feel - there's a real culture of casual consumption going on. You could even say dependence but of course nobody in legitimate mainstream culture likes to discuss 'substance dependence' because they think you're accusing them of being a smackhead. But many other students I have seen - and indeed their parents as well - are wholly dependent on a pot of coffee in the morning to get their engines warmed up. We take such a casual attitude to consumption of things like caffeine and alcohol when, really, they are just as biotoxic as many controlled substances (but that's an oft travelled and tired point to make, I admit).
Funnily enough caffeine affects me way more nowadays, after 3-4 years of the 'student' experience putting just about every drug under the sun into my body. I guess it's easier to compare the stimulant rush and see similarities with cocaine, amphetamine, Ritalin-variants etc (and a strong shot of caffeine will give you just the same temporary mental lucidity and singular focus as these drugs).
Oh and I'll take a nice strong tea or coffee over an energy drink, any day. Casual caffeine use is one thing but diabetes from massive and constant sugar intake is another.