It's been discovered that coffee in moderation is good for most people, especially when taken with other substances (in certain cases.) The following article is not the whole story, but it is a good start.
"Coffee not only regulates the liver qi, but also purges the gallbladder. In fact, modern research in Chinese medicine suggests that most herbs that regulate liver qi have this effect on the gallbladder as an integral part of the qi-dispersing action, but some herbs have greater gallbladder purging effects than others. The liver (and gallbladder) regulating properties of coffee explain its ability to protect against formation of Gallstones and its ability to alleviate constipation. This action has been attributed to chlorogenic acid and other constituents found in coffee."