Worth the update from El Capitan yet?
Between Picture in Picture mode (though, it only works on so many players), universal clipboard, the changes to iCloud Drive, tabs in stuff like Pages? I found it worth it.
iMessage changes aren't groundbreaking or anything, Siri I never touch, Apple Pay is fine but I've never used that either. And apparently you can now unlock your Mac with your Apple Watch?
Some annoying stuff currently with Photos, bluetooth is wonky for wireless mice with this last update (so if you have one, maybe wait 'til the next one). I've had some funny issues where even right clicking on an app I want to install, they try to tell me it's damaged, so I had to use a terminal workaround to disable a thing, then enable again afterward. Oh, and Safari still ain't shit, so I've been using the Tech Preview since the betas on my rMBP 13" mid 2014. ¯\_(ツ

_/¯
It's all about what effects you, what increases your own productivity, right. I mean, I'd upgrade anyway. If you choose not to, though, they're still throwing up security updates for El Capitan, p sure, so.