I was addicted to caffeine in college as I often had to pull all-nighters to finish projects. I found that a two-liter of Mountain Dew was just the right amount to keep me up, but not so much that I got the shakes (was an architecture student so I needed to still be able to draw, and Vivarin and NoDoz gave me the shakes). Once I graduated I gave it up cold turkey and I'm glad I did. When I see the dependence that those around me have on it, it makes me appreciate that I no longer need to rely on caffeine. On the rare occasion though that I have a can of caffeinated soda, I really get wired, in a not so fun way (seems to affect the intestines too
), so that doesn't happen too often!