Coffee? Today, question isn't a binary yes or no, but rather a quantifiable cups per day. With a little math, you can optimize your daily caffeine intake in both the long and short termto maximize your productivity. In a fantastic article dating back to 2007, Arvind Narayanan illustrates a highly simplified (yet generally accurate) method for optimizing your caffeine intake with your circadian rhythms for maximum punch! Here's a quick excerpt from the article. Enjoy!
Over the long term, consistent caffeine consumption is as good as nonconsumption, because of (you guessed it) tolerance. Is there a better strategy? Of course there is. Periodic abstinence lets adenosine levels return to normal. With complete abstinence, it takes 5 days to reach adenosine normality; conservatively, and with imperfect abstinence, a week or 10 days may be required. (Quitting is hard!) For most people, work involves a natural cyclic pattern of crunches and lean periods, and moderated coffee consumption to reflect this pattern will let you enjoy its cognition-enhancing effects more-or-less permanently.