Mike,
Having Native Graphics Driver for Mac OS X is important for Mac User, since a X11 Apps doesn't behaves like a "normal" Mac OS X App. For instance, there is no icon for it in the Dock, which is indeed important. Moreover I am not convinced about the x11drv speed on Mac OS X. I didn't investigate much here, but the DGA extensions seems to be capital, and I don't think we'll get DGA on Mac OS X due to its windowserver architecture.
Any way it is exciting to have an other driver other than x11drv and ttydrv ;)
Pierre