We always have our phones with us, so putting phone/3G would be somewhat a waist.

I see the benefits: you want to surf the net so you put you mobile's SIM in and with the 3G your good-to-go.

But if you think about it, 3G is somewhat too slow. I mean if that was the purpose, you will have only gained flash/screenestate since the 3G will be the "bottleneck" of the experience.

If you dont put a 3G in, you could still tether via Wifi/bluetooth from your device but again you would be "bottleneck" to that limited connection.

I think if you wanted to make this a mobile internet device and compact computer, you would look for more than that.

I think it would be better if you just connect via Public Wifi (which is happening throughout some cities like Taiwan/London). But what I would really aim for is WiMax/4G. It is fairly new but there has been great interest in its field and somewhere in the future I think 3G will be limited to "dumber" devices as carriers begin to support it and provide pre-paid accounts or planned connections.

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Edit:
I just saw those tablets. I don't feel compelled to buy either. If you are going to make a device larger you need to compensate with new features. Those tablets already have KIRF phone companions which could do what it can do. All you benefit from going big from the phone companion to that tablet is larger screen, more memory, maybe more battery life.

I was thinking of making a device which actually makes sense to upgrade from the smaller size phone and the larger netbook. It gives you that large computer feel without destroying portability and battery life. However, its to complement your dumb/smartphone but replace your netbook. In the latter device's sake (Core i7) it would replace your need for a laptop and netbook!