One does a lot of bending over when performing other tasks, so I don't see it as an ergonomical problem here.
It's not that different from what we were doing before computers.
Leaning over a table to write or draw with a pen, it's the same as this table.
I'm more worried about the durability of such a device, especially it's resistance to scratches and smudges on the tabletop.
Also, at current stage it's too big and clumsy for home use. It needs a lot of space on the base of the table because of the projection system and all. Until they are able to make it "flat" and more portable, I don't see it becoming massmarket, certainly not something of a successor to xbox360.
What will Apple show next? Didin't they have some patent for a multi touch interface. I guess it was aimed more at portable devices such as next gen iPods, and lacking the identification of objects placed on the surface, which I think is the coolest thing in the microsoft table.