Well I don't really believe it, but I think that I've actually seen a mythical creature with my own eyes. An emerald-scaled dragon from ages long gone. A winged fairy flitting from flower to flower collecting nectar. A unicorn with shining **** glimpsed through snow-white trunks of a forest of beech trees.
For the first time in the history of the Mac OS (as far as I know), there is an official Apple-sanctioned option to turn on auto-hiding for the menu bar.
System Preferences --> General --> "Automatically hide and show the menu bar"
When my Menufela "haxie" stopped working several years ago I had already long since given up on ever seeing an official Apple-supported way to auto-hide the menu bar. But there it is in El Capitan, staring me in the face.
This is the Holy Grail for those of us who like to minimize visual distractions and unnecessary stuff being displayed on the screen, but still want to work with multiple windows at the same time and use all available screen space.
No, going fullscreen in a single app that is capable of going fullscreen is not the same thing. Not the same thing at all.
I very much hope that Apple will keep this feature available in El Capitan and all versions of OS X henceforth.