I tried the mentioned extension on my Linux desktop and have to say that I'm not really impressed. If performance was so poor on a desktop, how much worse will it be on the tablet?

Gecko should rather be made render to a server-side offscreen pixmap, which can then be rendered quickly on screen, including zooming and kinetic/inertial scrolling. Quiver e.g. demonstrates very well what the tablets are capable of with the XRender features of the X-server.

But I'm just dreaming...