These may not be ground-breaking changes to apps and the operating system, but this collection of small additions makes using El Capitan a little faster, smoother, easier and better. And the under-the-hood technologies lay the groundwork for richer apps down the road. It's these usability iterations found throughout El Capitan that make the biggest difference.
As with any major software upgrade, make sure your apps are supported before moving to El Capitan. If you're hesitant about upgrading, it isn't a bad idea to hold off a while and see if any major bugs are discovered. But because this version was vetted throughout the summer with a public beta program, I'm not expecting any showstoppers now that the final version has arrived.
In a nutshell: El Capitan does what it is designed to -- streamline OS X across the board, making it more efficient to run and flat-out easier to use. It's free, it runs well and I recommend it.
If you've decided to take the OS X 10.11 plunge, make sure to back up your system before upgrading. Apple's built-in Time Machine feature works well -- all you have to do to turn it on in System Preferences and plug in an external hard drive; the Mac will automatically ask if you want to use it to start a backup. (Alternatively, there are other third-party utilities like SuperDuper that offer more control if you're more technically minded.)
This is also a good time to run a diagnostic on your Mac's file system. To do this, restart your computer holding down the Command and R keys at startup and then use Disk Utility to check for unseen problems. You can also use Alsoft's DiskWarrior, a much better third-party alternative. My feeling is that DiskWarrior is the rare piece of software that should be in everyone's arsenal, regardless of experience level.
Once backups and diagnostics are out of the way, El Capitan can be obtained from the Mac App Store and will download to your Applications folder. To manually install it, double-click the installer icon, enter your username and password and select your target destination. The installer does the rest.
Here's an important point: If you have more than one Mac in your home and/or limited bandwidth for downloads, you can use the same installer on multiple machines. Copy the file from the Applications folder to another Mac via AirDrop in a Finder window or transfer it to an external disk. Just sure to do this before running the El Capitan installer. If you don't, when the installation is complete, the Installer will delete itself.
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