I'm sticking with 10.9.5 on my MacBook Pro. I also have an older iMac, but haven't upgraded that either. I don't have an iPhone, or any other Apple devices to connect to, and don't plan on getting any. I don't use many of the application programs that came with this computer, like iMovie, iTunes, Garage Band, Face Time, etc. They can keep Siri. Who the hell wants to listen to that? When I upgraded to Mavericks, I had a few third party apps that the OS didn't like. I managed to get them to work, but don't want to be bothered again with any incompatibility issues. This OS works fine for me, and if it ain't broke...it don't need fixin'.
On the other hand I’m at 10.68 with no plans to “upgrade” short of buying a new mac if old one dies.