The E19 RC3 release most notably features the rewritten Wayland compositor that was talked about on Phoronix earlier this week. The Wayland compositor rewrite for Enlightenment reduxes the memory footprint along with the code-base size and at the same time lowers the rendering complexity. This new version also supports Wayland clients inside X11, wl_shell/xdg_shell protocol support, initial support for standalone Enlightenment Wayland, and has no hard requirements on X11. This new compositor is still considered unstable and doesn't yet feature XWayland support.
E19 RC3 also boasts translation updates, tiling improvements, various bug fixes, improved system tray handling,Ibar menu reliability improvements, and various crash fixes.
More details on E19 RC3 can be found via the Enlightenment.org release announcement.
There's also another update on the state of Enlightenment via the E19 release manager blog.