A Venerable Bede links to several sources showing that at least in the United States, believers tend to be happier, healthier, and more charitable. The pseudonomyous Theodore Dalrymple has something similar to say. (hat tip: John C. Wright)
In my own experience, most of us religious people are pretty lousy people, no better than the common run of everyone else, but the few saints I’ve known have been disproportionately religious. The best use to which we can probably put these kinds of evidences is to reflect on the kind of person we could be given the excellences of our religion and the power of Christ’s grace and compare it to the kind of person we are. We might ask ourselves if Christ died on the cross so we could be decent Joes.
I suppose we could also put these things to apologetic use. I don’t think they’re hard proof, since quite likely people who find it easier to be good find it easier to stay believers (correlation does not equal causation, in other words). But they do create a space for belief and a challenge to unbelief. I suppose one could also use these things in a President Hinckley kind of way–while not denying how far onward we have to go, taking satisfaction that with all our trying we have managed to move a little.