El Capitan’s “SIP” might render your apps useless.

El Capitan is like every other version OSX and works well in all basic capacities. Apple added bells and whistles, as usual.

Apple also added SIP “System Integration Protection” to make a safer OSX, I guess. But SIP killed the operability of a great many of my music and audio production apps and now I’m scrambling to find a copy of OSX 8 or 9 so I can dual-boot. It is always better to move forward with software instead of hanging back... but "scramling to find alternates" is never fun.

Basically, double check compatibility of your software before you upgrade, especially if you are using audio/visual production apps. Many such apps have, thus far, required root access: El Capitan will deny it to them and may limit, or end, their functionality.

Seth Asa about OS X El Capitan