I have a feeling that the carriers will force users onto a tethering plan for something like this, like what AT&T did when the first Atrix dropped. Although Verizon hasn't forced this with their Moto phones and the docking station, and I believe AT&T has moved away from this.
All in all I think it's a great concept but it's just a little too much money for all the bells and whistles. With over $900, you can get yourself a nice phone and tablet and use Wifi tether and call it a day. Or you could get a Galaxy Note and forgo carrying around the clunky hardware that comes along with it.
I hope Asus succeeds, but I won't be surprised if it's a flop. I doubt Verizon even gets this anyway. I don't see a reason to get this phone over the GS3.