"Praying for other people to recover from an illness is ineffective, according to the largest, best-designed study to examine the power of prayer to heal strangers at a distance." (from the Washington Post).
They then have this choice disclaimer: "The researchers cautioned that the study was not designed to test the existence of God or the benefit of other types of prayer, such as praying for oneself or praying at the bedside of friends or relatives. They also did not rule out that other types of distant prayer may be effective for other types of patients."
So, if you're agnostic you can happily remain so. And if you're a believer you can continue to believe that God works in mysterious ways, ways not amenable to discovery in a clinical trial.
What was more interesting—the study was not double-blinded—more of the patients who knew they were being prayed for experienced complications. In fact, prayer had a negative effect, in the sense that there were more complications!