I think caffeine is great in the right dosage and setting (recreational). I don't advise using it at work if you are after high productivity http://www.trinity.edu/jdunn/spiderdrugs.htm
On the other hand, spiders DO build web 'sites' and await food delivery...
From persona experience i either have to go a few days without or drink my third cup (drip brewed) of the day to get anything noticeable.
No jitters but if I take all 4 at once I get a pretty unpleasant "coming up" feeling for about 15 minutes. I usually just have 2 a day, and I'd recommend people start with 1 just in the morning.