Open Source DHTML Abstraction Layer

I found an interesting library under the LGPL that is a DHTML abstraction layer to simplify cross-browser and cross-platform DHTML programming. It is called X. I think it was used to make the Rock Star Fish site I compatibility tested in my last post. The reference manual lists alot of very interesting objects that should make DHTML programming much easier cross-platform. Does anyone here have any experience with this library? How about other open source cross-browser/cross-platform DHTML abstraction layers? I've seen other ones but they always seem to impact performance; this one doesn't seem to have that problem.