I'm also the kind of person who can drink coffee at night, or can have a couple of cups of coffee after dinner, and not notice any effect on my sleeping. I'm definitely not addicted, because I rarely drink coffee on weekends - so the last three day period I went without coffee was this past weekend.

I usually go to bed between 9:30 and 11:00, and I drink my coffee black if that makes a difference. Maybe it's all the sugar that's keeping people up (or it could be that different people have significantly variant biochemistries; who knew?)

edit: I knew I remembered seeing this...

http://bodyodd.msnbc.msn.com/_news/2011/09/02/7562142-coffee...

http://www.sciencedirect.com/science/article/pii/S0195666311...

Abstract: "We explored whether caffeine, and expectation of having consumed caffeine, affects attention, reward responsivity and mood using double-blinded methodology. 88 participants were randomly allocated to ‘drink-type’ (caffeinated/decaffeinated coffee) and ‘expectancy’ (told caffeinated/told decaffeinated coffee) manipulations. Both caffeine and expectation of having consumed caffeine improved attention and psychomotor speed. Expectation enhanced self-reported vigour and reward responsivity. Self-reported depression increased at post-drink for all participants, but less in those receiving or expecting caffeine. These results suggest caffeine expectation can affect mood and performance but do not support a synergistic effect."