I personally - and again, this is just my personal opinion - would rather they leave the dialog unvoiced. There's no replacement for how you voice it in your mind, and it echoes games like Baldur's Gate and Icewind Dale, that did beautifully with unvoiced dialog (the only voiced parts being cutscenes).
I wouldn't complain if they voiced it, but I think the game can stand beautifully on its own without it.