I've never understood how anyone could be at all convinced by the "free will" defence against the problem of evil. It seems obvious that any cosmic designer did a shockingly poor job of designing us to be free agents. There are all sorts of barriers to human choice and free action that no perfect being could tolerate. Let's call this "the problem of unfreedom".
Here's the problem: humans are not ideally free agents. Due to our imperfect biological design, we suffer a variety of internal maladies -- from cravings and addiction to mental illness and simple irrationality -- that impede the rational exercise of our will. Our brains are far from optimally designed for rational decision-making. If God existed, he would free us from the bondage of addiction, bias and other mental defects.
Note that we had no choice over our own design -- our initial desires and predispositions. When we are moved by built-in desires that we wish we didn't have, this is a violation of our autonomy as free agents. Yet we are limited in our ability to shape our own desires. We can't change our innate dispositions through sheer force of will. A perfect God would have given us this ability -- to simply purge ourselves of violent, selfish, or lazy inclinations. Our bad design is not our fault, after all. The bad decisions and behaviour caused by this bad design are, likewise, not wholly our own responsibility. If humans had been created with the values of autonomy, self-creation and responsibility in mind, we would be very different creatures.
Again, every flaw we have was built into us (at least as a disposition ready to manifest itself upon exposure to the wrong environmental influences). Why would a perfect being do that to you? Even assuming that we have free choice within certain bounds, those "bounds" are not the ones that any remotely benevolent designer would have set. Clearly, we are not "designer babies".
One day, I hope, biotechnology will advance to the point where we can improve these flaws ourselves. But the very fact that we need to "play God" indicates that the job is vacant.