Yes, it may seem like you just updated your Mac OS to Yosemite. Guess what? There is a new version named El Capitan.
Yosemite was a big change. Lot’s of things looked and worked differently. El Capitan is modest in comparison. Notes is updated to include some Evernote type capability. Spotlight search is more intelligent. You can easily split the screen to run two apps side by side. There’s a new default font, and other modest changes.
I upgraded my computers about two weeks ago and have not had any issues. I have seen one major issue report, however, and that is only if you have upgraded your version of Microsoft Office to 2016. I am guessing that most readers have not done this unless you have a Office 365 subscription. There have been reported problems.
I recommend upgrading to El Capitan unless you are an Office 2016 user.
Here are two good reviews on El Capitan: