Earlier today I updated my performance-centric TwentyTwelve child theme to fix a problem with the mobile navigation (due to the fact that TwentyTwelve changed the menu-button from a
h3 to a
button, which required the navigation JS which 2012.FFWD inlines to be updated as well). You can download the update here.
This update “officially” marks the end-of-life of this child-theme. Although a lot of optimizations can be done on a theme-level, I prefer focusing on tools like my own Autoptimize, which not only optimize code spit out by the theme but also any CSS/ JS introduced by plugins or widgets.