The headline is a little misleading. For regular and heavy coffee drinkers, the study suggests that a cup of coffee merely brings the person out of caffeine withdrawal, and does not provide any stimulation. Since caffeine withdrawal makes you groggy and less alert, it means that regular caffeine drinkers have to consume caffeine just to reach the level they would have already been at if they weren't consuming caffeine regularly.

For people who don't currently have a tolerance for caffeine, it most certainly does provide stimulating effects.

It also seems like the study gave participants the equivalent of a single cup of coffee. If you need more than that for your buzz, looks like you'd have been out of luck.