For speculative purposes, a level of tesselation of 2, allows my PIII 960 + AIW Radeon get > 30fps on this demo. So if Nvidia can emulate this via drivers, I don't think you'll be looking a very good framerates. Considering I'm getting 30fps with two figures and black background, I can only imaging how terrible the performance would be in an actual game environment.
Going higher than a tesselation level of 2 brings my rig to its knees - single digit framerates around 5 fps.
Without truform, I can pull 500fps on this demo.