I used to drink redbull back when it first came out, I'd get one in the afternoon when I felt the 3:00 slump coming on. It worked. Or maybe it was mental. I don't know. But once I heard that people were mixing it with Vodka I got grossed out by the thought and couldn't drink it at all any more. Haven't had one in over 6 years.
Coffee on the other hand, I've been drinking since I was 18, fourteen years now. I stopped once while on Atkins for two weeks. Hell I tell you, HELL. Once I passed the first say 5 days of no caffein, I felt incredible. I was sleeping better, I was dreaming, and I was waking up completely READY to face the world. I'd never felt that way before.
Then I stopped Atkins, and started drinking my daily cup again.
THEN....again, I decided to give up the coffee. I lasted for a while, maybe a month or so, and again I felt a little better, but not as good as the first time I stopped.
As for bad experiences with coffee...when I first really got into a daily habbit, I think I was 19 or 20, coffee was going riiiiiiiiiiiiiiiiight through me. It was a wierd getting used to kind of thing I guess. And, believe people when they say "I haven't had my coffee yet, can it wait"....those day 2 headaches can be a bear.
Hope that helps....