If you don’t believe in free will, then you are more likely to lie.
People who are determinists really have less motivation to act morally than those who believe in free will, since they can’t do much anyways. They are less likely to be emotionally healthy.
I just listened to a podcast interviewing Marcel Brass, a neuroscience researcher. http://commonsenseatheism.com/?p=12153
Perhaps all of our discussions about predestination, determinism, and free will are a waste of time. We may never be able to prove things either way, but we can know the effects of different beliefs.
I have a lot more incentive to act morally now that I know I can’t just ask for forgiveness and the magic God will make everything better. I took a lot of comfort in the instant forgiveness and power of a being who could work all things out for those that loved him.
However, knowing that I have responsibility and agency in my choices helps me a lot more.