One big change that I've been working on for beta6 that doesn't have a ticket in GitHub is splitting PIE into multiple files... PIE.htc becomes a very small loader stub file, which goes out and fetches the other file(s) containing only the logic needed for the current browser (and maybe only the logic for certain needed features). Those secondary logic files will be hosted on a CDN by default (assuming I can find a suitable CDN) which will allow the bulk of the download to be served from a fast location with gzip enabled, something not all users are currently able to do themselves. There will also be an option to specify a custom location if someone doesn't want to use the CDN. Between the pared-down logic files (no need to serve IE6-8 code to IE9 users) and the fast CDN delivery, this should result in a pretty decent decrease in download time even with the extra HTTP request.