Would I trust one? Would depend on the person, but that would be regardless of religion or lack thereof.
Do they make society worse or better overall? Most make it better - difference is good for society - it promotes questioning, discussion. If nothing is questioned, nothing is learned. If nothing is learned, then society will cease to exist.
Some, however, do do their best to make Atheists look bad, and put people off by being overly aggressive in their stance - thankfully, they are a minority...though a reasonably vocal miniority.
Do I think that they are capable of having morals or not? Well, given that morals are not solely of religion's doing, of course I do. Perhaps, even more moral than some who claim to be religious. Why do I say that? Well, the measure of a person is NOT who they are when they think someone is looking, but who they are when they think NO ONE is looking. In many religions God or Gods are omnipresent - so, they are always watching, so those who are being moral only because God is watching - are they really moral? What would they do if they found God wasn't watching?
Also, I've met more than a few immoral religious people - of many religions.
Given that atheists do good for the sole reason of doing it - no other outside reason like pleasing a God - yes, atheists are capable of having morals.
As an Agnostic Atheist, I'm certainly trustworthy, I strive to make society a better place, and am a moral person. I just don't believe in God/s.