OS X 10.11 El Capitan was released about 2 weeks ago. It is a free upgrade and will run on any Mac that supports OS X 10.10 Yosemite. It will also run on many Macs that support OS X 10.6-10.9.  https://support.apple.com/kb/SP728

As with Apple OS upgrades of recent memory, El Capitan offers a handful of new features and enhancements, plus a variety of graphical changes… but in my opinion these include nothing substantial enough to warrant an immediate upgrade for most users. Being an early adopter comes with the risk of downtime, app problems, and printers or peripherals not working.

MY RECOMMENDATION…
For production Macs on OS X 10.9.5 Mavericks or OS X 10.10.5 Yosemite, I highly recommend against end users upgrading to OS X 10.11 at this time. Older Macs running OS X 10.6-10.8 should not be updated, period, unless done so by a qualified engineer.

My opinion on this will change over time as Apple releases El Capitan updates, and third-party developers release OS X 10.11 patches and drivers. Historically though, I don’t generally consider an OS stable until Apple has released the .4 or .5 update… so I likely won’t be recommending El Capitan to the masses until OS X 10.11.4 or 10.11.5 becomes available.

As a rule of thumb, upgrading from one version of OS X to another is not something I’d recommend in a production environment without a compelling reason or solid upgrade plan. Reasons would include a necessary application that requires a newer version of OS X, security concerns with older versions of OS X, or upgrading all the Macs within a workgroup to keep them consistent for an imaging solution.

Two important tips for early adopters:

  • Make sure that every single application that you use is patched to the latest version before upgrading, and while doing so also verify each application version is compatible with El Capitan. Upgrading OS X, and then dealing with applications not working because they are unpatched or incompatible, is a common mistake leading to hours/days worth of frustration.
  • Mac sure you have a full backup of the Mac saved to an external drive prior to upgrading (either with Time Machine or more preferably Carbon Copy Cloner). Upgrading OS X is a one-way path if you don’t have a backup, and those that experience major problems often wish they could just go back to the way things were. Having a full backup makes that possible.