This rather interesting article from the ABC News site made interesting reading. I have persistent shingles which is not severe, just rather annoying. I often take pain killers to reduce the pain but I find that a cup off coffee does much to reduce the impact of the pain.
Purely subjectively, what I found when the pain was at its most severe was that the coffee took the edge off the pain, or reduced the sharpness of the pain, and the pain killers reduced its severity. This article then come as absolutely no surprise to me. It would be interesting to see if any research has been done as to the effects of caffeine on the pain of shingles.