Hmm- well certainly it's not some radical new invention that is going to change RPGs as we know them. We are just taking advantage of the fact that there is only ONE character on-screen (not an entire party) so we can process the player's input faster.
I read on RPGCodex that someone said it sounds like a Roguelike game. I've only played a couple of those (years ago) but I do think maybe it does feel something like that.
Basically, since the player has only one character on screen to manage, we do not have to parse one-by-one through every character in a party. Because of this, we can streamline the process so that you can just tell your character "perform this action", then the computer instantly decides how each enemy on-screen will respond, then the animation cycle for that round plays out so you can see the results. It's really just kind of a real-time system that is segmented into turns, so you can get that kind of flow when you just want to hack away at something and allow the turns to flow quickly...but you can also stop what your doing, analyze the situation and make tactile decisions (if that is your play style). Remember- nothing happens until you take a step, fire an arrow, or drink a potion. When you do that, the computer decides what the rest of the game world will do in reaction to your input. Actually, the game remains in this pseudo-paused state most of the time waiting for your input.
The problem is that for Book II we will have to go back to a more traditional turn-based system because this system does not work if you have to issue commands to multiple party members. This system is really just a by-product of only having one on-screen character to deal with.
