Well, I think it rather depends.
MS isn't exactly promoting a controller less interface for the sake of being a controller less interface.
Their push with Natal is a control scheme (in this case using gestures and body movement) that is more intuitive/natural for someone that has no experience in gaming.
I think that's something a bit hard for anyone on this forum to visualize since we've all used controllers of one sort or another so much that it has become the natural way to interact. Mouse and Keyboard for FPS for example is extremely counter-intuitive and unnatural when you first start to learn it. It's only through repitition and persistence that your body and brain adapt and make it natural.
All that is to say that what seems like a natural method of control for us here on the forums might be completely counter-intuitive to the primary market MS is targetting with Natal.
That said. I'm pretty sure if there was a physical device "add-on" that MS feels fits into this natural control scheme they'll consider adding it.
PS3's system is definitely catering more to the crowd that is already at least somewhat experience in console gaming. As witnessed by their making PS3 Wand similar to traditional controllers and leveraging those console reflexes that people have picked up over the years while console gaming.
MS is going in a totally different direction by primarily targetting those people with very little or no experience with console gaming.
If they execute well on this, it's very likely that those with no console experience will feel much more at home and at east with Natal than those people with lots of console experience. In that case, they've hit their target right on.
In other words, I think we have to accept the fact that PS3 wand is more targetted at the people that would frequent this forum for examle. While Natal is targetted at us only indirectly or possibly not at all...
Either way I'm still far more excited by Natal's controllerless experience than any scheme using a physical controller as the central piece of the control scheme. Especially as the Natal scheme translates well to devices beyond consoles. Computers, DVD/BluRay stand alone devices, TVs, Air Conditioners, House Lighting, etc...
In other words, depending on implementation, the Natal concept can easily be expanded to universal control of just about anything. Whether it ever goes there, who knows. But I like thinking about it. Coming home and using a hand gesture (a wave for example) coupled with saying "Lights on" (combination to avoid inadvertently activating lights on when not intended) to turn the lights on would be inestimably cool.
And since Natal can already "see" in the dark, it would be possible to implement assuming Natal is also useable with a computer.
Regards,
SB