Yep, lots of progress. I’ve made two meteor packages that accomplish the following without hacking core:
Except Meteor config stuff which would make things very wonky on the unlikely chance it arrives after the big mothership.
Inlines one user script file into the initial html payload
Removes all unused CSS selectors, rules, and media queries from all your aggregated CSS based on a user-supplied list of unused selectors and inlines this lean CSS into the initial html payload
This dramatically shrinks your CSS if you’re using a framework like Semantic or Bootstrap and styles the page perfectly on first render without waiting for massive CSS file–which is still coming in case your unused list isn’t perfect. You can copy-paste a list of unused selectors from a tool like Chrome Dev Tools Audits --> Unused CSS Selectors.
It’s working well in my development site, haven’t gone live yet. If anyone is interested in these packages I could put them up on Atmosphere but they are far from polished. As it is now, it assumes your are doing SSR with React (ie. requires react, react-router, react-router-ssr, react-helmet).
edit: Also handles icons fonts so you can use a custom iconic font service like http://fontello.com/ (free) to build a font with only the icons you use and embed that directly in the CSS in the initial html so all your icons are there for first render without downloading an external font file.