What this means for me would be drink coffee while coding and don’t drink it while thinking about design and while trying to study the requirement documents.
So:
Use caffeine for short-term performance on a focused task (such as an exam).
Avoid caffeine for tasks that require broad creativity and long-term learning.
(Disclaimer: The greater altertness, larger short-term memory capacity, and eased recall might make the memories you do make of higher quality.)
via Less Wrong: Coffee: When it helps, when it hurts.