Hmm, I am sure I am in the minority, but I actually like the look of the flat lighting. It reminds me of an old overexposed polaroid, and (at least in my mind) it seems to be more an artistic expression than a limitation within the game. It seems to fit well with the old newsreel footage, aged documents and pictures used to tell the story. I don't really get the impression that Insomniac is going for hyper-realism, and is instead aiming for something slightly cartoon like.
This may be do to my experience with the R&C series. I have only seen videos online and the actual in-person experience may indicate that the game is trying to present itself as something more than I assume, and that in that attempt it leaves itself lacking. Whatever the case may be, I picked up my beta voucher today and I am very excited to start playing this in the next few weeks.