While coffee may have an adverse effect for folks who have Type II Diabetes, folks who might otherwise be at risk, but who have not yet developed this form of diabetes, are likely to find moderate (*meh* ~4 8-oz cups of coffee–NOT some Starbuckian monster drink loosely based on coffee) to be beneficial.
With the growing incidence of Type II Diabetes in the US, one might wonder just how much worse the “epidemic” might be w/o coffee.
Then, of course, there are some other well-known (to coffee aficionados, at least) benefits referenced at the link above: amelioration of the effects of Parkinson’s, protection from liver cancer and cirrhosis of the liver, cardiovascular benefits, etc.
Do note, that for optimum health in otherwise normal, healthy individuals, 48-oz. of coffee/day is right about the upper limit. Strangely, that seems to be about the upper limit for optimum health effects from beer consumption, too. . . (though that would be consumption over time, with meals)
Moderation.
Lastly, of course,