Trying to keep things as simple as possible:
I doubt free will, and here's why. No one knows if quantum indeterminacy translates on a larger scale to living beings.
But it isn't looking good for free will I'm afraid. Atoms, which is the next level from sub-atomic particles, act in extremely predictable ways. It's called chemistry, and it's strictly mathematical, which means it's predetermined.
How someone can think indeterminacy somehow translates into complex biological organisms is a little bit a stretch, considering how predictable atoms are, and considering that all cells are basically made up of atoms.
I think our brain creates this illusion of choice, when there isn't really one. Neurological studies have pointed out that electrical activity in certain brain regions PRECEDES conscious activity. In other words, first your brain is spinning its gears and THEN you make a 'decision' or have a thought or feeling.
I'm not entirely sure why our brains do this to us. I see no evolutionary reason why living things would 'need' to feel like they are in control. It's a damn convincing illusion, since someone could easily say "but I'm choosing to wave my arm around right now, as we speak. Is that not free will?" But then I could tell him that his act of moving his arm and trying to prove to himself and I that I'm wrong, was determined and was reaction based off me telling him that free will is an illusion.
It's confusing and unintuitive, mainly because the illusion is making it almost impossible to even conceive of such a notion as determinism. It's easy for us to look at a volcano eruption and say it was predetermined by physics. It's even easy for us to look at animal behavior and say it was predetermined by instinct. But human beings? Hell no. And that is because human beings are too complex for us to accurately predict. There are just too many variables to even make sense of it.
After all, how can a human being, with the limitations of their brain, possibly have complete understanding of all human beings and make predictions? It's like trying to use the brain to map out the brain of not just ourselves but everyone else too.
Predicting human behavior will always be outside of our grasp, but that doesn't mean that it's not predictable. I suppose the only thing that COULD do such a thing would be an extra-terrestrial far beyond us.
But then, of course, everyone will call you stupid for even suggesting such a thing. "of course we have free will, stupid!". What appears self evident to the layman and even the educated, might very well end up being bullshit.