Using separate, uncompressed filesIn debug mode, our app brings in each JS and CSS file seperately, uncompressed.
This is not a scientific test because in 'debug' mode the back-end is (much) slower as well as the front-end. But note the grey bars: those are 'blocked requests' i.e. the browser has opened its max sockets to our webserver (usually 6, browser dependent) and until one of those is freed up, it can't get the next file.
Also unscientific because this was also using 'jquery-ui' already minimised, meaning the filesize difference would be more significant otherwise.
ResultsA reduction from 17 requests to 5, from 181kb to 124kb and from 13 seconds to under 1.5 seconds.
NotesResults exported with the wonderful NetExport plugin for Firebug.
The technologies doing the magic that haven't been mentioned are Assetic and Symfony2.