Finished reading it? Good. It seems like it would really speed up rolling, but removing the models all at once will be somewhat anticlimactic, I think. You already know they are being removed, you now just need to pick over the corpses- which is fine for Tyranids. I enjoy the "Will the marine shrug off this shot?" tension. I hate just removing models when they are instantly killed or have no save. It's harder to picture in my mind "the cinematic" (in 5th Ed.) when I'm just calculating who is coming off the board.
I'm definitely going to try both types (the rule book and 3++ speed rolling) and then see how I feel about it.