While I admit I am still in the "Wonder Years" (MS 1 & 2) (loved that show), I recently quit coffee and am amazed at how good I feel now. I sleep like a baby, and tend to have a much more even energy distribution throughout the day, as opposed to my coffee days when I would be about to pass out after lunch if I didn't have a cup.
Hope I can keep it up when I hit the clinical years.