Dolch Touch-Controls makes the most durable touchscreens using infrared (beam breaking) instead of resistive or transflective.
They also make retrofit frames for plasma–which would be ideal for a table due to its size.
Also look into tabletop projection using Siemens Sivit “virtual touchscreen.” It “sees” where you touch the projection, regardless of the projection surface. This is in use at the Prada Epicenter store in NYC and it’s killer.
http://w4.siemens.de/FuI/en/archiv/zeitschrift/heft1_98/artikel07/