I'm not familiar enough with Emacs to comment about the performance of overlays, etc., but I'm surprised that processing *text* can be so CPU intensive.
These days we have games running with millions of pixels and shading or whatever (some use the GPU of course), and browsers with fancy Flash animation and dozens of tabs open and spreadsheets with thousands of cells and word processor documents with hundreds of formatted pages on dual cores and quad cores with GB of RAM. Is this performance overhead just a result of poorly-scalable overlays, rather than an inherent shortcoming of Emacs and/or org-mode?
