I don't drink coffee. I have. Sometimes I have tea when it's around. They're both very successful at doing absolutely nothing for me, so much so that up until a couple years ago, I wasn't convinced that everyone is just bullshitting about it. Much like when you'd go to a house party in high school and people who've had very little (or perhaps unknowingly, nothing at all) go on about how drunk they are.
neither. I have realized that caffeine dulls my senses (and it makes me care less about things in general). I drink tea once-in-awhile, but generally try to avoid anything with caffeine. I also sleep much better at night.