Went cold turkey on caffeine a couple weeks ago after sustaining a 3-6 cup daily intake for months. Been feeling unmotivated, taking the occasional mid-day nap, and having unpleasant thoughts along the lines of 'where's my god damn coffee' when urges went unfulfilled. The first 3 days were lazy, headache-clouded, and unproductive. After that, though, I started to notice that I felt like working on projects in the afternoon and evening. It's a minor change in mood that's led to a major change in behavior, at least in the short term. Worth the costs, even if only for a brief change of pace.

Tried it; the most awesome part about not taking caffeine anymore, for me, was the fact that one cup of coffee would then do as much as five previously. The downside is that I did not, in fact, feel less groggy generally, even after adjusting. Even with my high tolerances a caffeinated life is more energetic than a non-caffeinated life. I'm sticking with caffeine.