I don't drink coffee and I've never liked the taste of it, but after watching this from Dr Aaron Carroll I'm thinking I should try to learn to like it. That's especially true since I have problems with daytime sleepiness and a medication recommended to me for that (which it turns out I can't take anyway) has some potentially serious side effects and (at least according to Consumer Reports) has never conclusively been shown to be work any better than coffee for that.
To summarize, it turns out that there has been quite a lot of research on coffee and health. Unfortunately, it has generally not taken the form of randomized controlled trials, which would be ideal but for obvious reasons not easy to carry out. Instead the studies have involved looking at how much coffee people consume and how healthy they are over time. Surveys of these studies, combining the results for very large numbers of people, suggest that moderate coffee consumption is associated with overall better health and lower rates of disease, including cancer, heart disease, and stroke. See the video above for details.
I feel I would be remiss if I didn't also include the following short documentary illustrating a potential benefit of coffee from a non-medical standpoint, though I have some doubts about its scientific accuracy:
(This remains my favorite episode of Film Riot, a web series about filmmaking and special effects that also has an appealing sense of humor.)