But really, let's leave God's omniscience out of it for the moment.
Think about what free-will is actually supposed to be. It's a central concept in islam - its justification for punishment, its attempt at holding our souls responsible for our actions. Muslims recognise that there are constraints or limits on what we can do. And from a scientific point of view, we know things are either determined or random (or a bit of each, I guess). Unless I'm missing something, there is no other option. If something is determined, then the responsibility for an event lies at the determiner, the first cause/ prime mover - in other words, God. If God wants punish someone for an evil you commit, he will have to punish himself. If it's a random event then we cannot aportion blame.
Most pople talk about having 'choice'. "I chose to eat a bacon sandwich", though it's immediately obvious to anyone who spends a minute thinking about that statement that it was determined by a variety of factors (how hungry they felt, what they'd had earlier, what nutrients their body was craving, what was available etc) and if the universe is deterministic then there was never any alternative. If the Universe is indeterministic then I guess there were possible alternatives, but the one realised was so by chance and probability. Either way our 'souls' are blameless.
Enter free will, which supposedly renders us blameable. But what exactly is it supposed to be? The way it's used makes it synonymous with ignorance. You can see certain influences, certain detemining factors, and beyond that everything is done by 'free will'. "Sure I had a cheeseburger because I was hungry and had just seen an ad for it, but that only influenced me, I still 
could have chosen not to". What on earth does this mean? 
Consider two people, physically identical in every way, had exactly the same experiences, to the finest detail, and are faced with the same choice. If 'free will' exists it is conceivable that they would make different decisions. How? As soon as you introduce an influence, a reason, a 'because'... we are back to where we were - causality. If there is no 'because', then how is it any different from randomness? Things are either caused or chanced, and neither is free-will.
Free-will isn't a concept, it's just the process of apportioning blame/credit. It's the point at which you cut the causal chain (or single out the probabilistic event) and then name 'choice'. Even God cannot be said to have free will. He is supposedly unaffectable and needless, what would cause a desire to manifest itself in such a being? If he wants... if he wills... then it's as if he is subject to laws and circumstances that he had no role in assigning to himself. An omnipotent being would only be truly free if he rids himself of his last bounds - his desires... he will be free if he destroys his will. But 'free will'? It makes as much sense as a square circle to me.
Yet people accept, and I assume understand, the concept of 'free will'. What am I missing? 
(Note: I use free will in the Muslim sense.)
*waits for z10 to disagree"