One more note on older browser support. We need to define "support". If it means that the pages render the same in older browsers as newer ones, then we're never going to get there. If it means "usable", then I think it can be achieved.
Multi-column CSS layouts can be built that will render very simply in older browsers, by using various css hiding tricks to provide a basic stylesheet for the older browsers, which is then overidden by an advanced stylesheet for those browsers that support it.
--Steve
