They affect me. Regular energy drinks don't affect me much more heavily than a cup of coffee or a bottle of mountain dew, but I am never drinking a 5 hour energy again. I've got Tourette's syndrome and ADD, which is relevant because the amphetamine derivatives used to treat ADD interact badly with my Tourette's, making me bounce off the walls. Caffeine doesn't do it, but 5 hour energy does, which makes sense once you realize that one of the chemicals in the "energy blend" is a bloody brain chemical that was originally isolated as a stroke treatment in Japan. In most of the world, it's a prescription drug and a powerful stimulant. In the US, it's one of those "dietary supplements" that the FDA doesn't bother to regulate, and I learned the hard way that that one happens to work.
Edit: Oh, by the way, 5 hour energy is less of a problem than, say, Ritalin for me, but it affected me roughly the way ritalin does a person with a normal reaction to it, and I was physically unable to sleep for 14 hours after taking it -- which is impressive when you consider I drank the thing after 10:00PM at a LAN party that ended eight hours later, after having been up all day.
Edit Edit: And I can normally get to sleep no matter how much caffeine I've had, it just takes the edge off of the drowsiness for me.
[/small]