The latest operating system by Apple is coming tomorrow. As a professional who relies on technology, namely- Final Cut Pro, I am looking forward to the accelerated Core Animation and Core Graphics all thanks to Apple's new graphics technology- Metal which promises to "boost system-level rendering by up to 50 percent, and efficiency by up to 40 percent, resulting in faster graphics performance for everyday apps.* Metal also takes full advantage of your CPU and GPU, delivering up to 10 times faster draw call performance for a richer, more fluid experience in games and pro apps."
It is my experience however, that you should upgrade to a new OS very cautiously as many developers are still working toward making their apps and plugins work with the latest operating system. Thankfully, the past few years Apple has been releasing developer beta releases so they can get a jump start on the release, making upgrading a lot more smoother for users.
My recommendation is to not upgrade your primary machine until you know for sure all of your 3rd party applications, plugins, and effects are compatible AND upgrade after another Pro-App update as well. After all, you can't make money on a machine that doesn't work properly because Final Cut Pro X uses the OS for many of its core tasks. If you're like me and curious about El Captan, you can read more about the free upgrade here and upgrade a secondary machine like a laptop, to get a feel for what the future holds.