Yeah, it's mostly social media B.S. and Siri. Although the application tabs intrigue me to no end. I use Pages so much and regularly have so many documents open at once, that tabs make a lot of sense, although that is yet to be tested by yours truly, since the Beta gave my wife's email a swirly. Unhappy wife, unhappy life. So, El Cap will remain until I am confident multi-user email settings are getting the shaft-ola!
Keep in mind, once the OS is "free", there is little drive to add amazing new features. If this OS was $19, people would be fuming! "Nineteen dollars for Siri? Are you joking?"
Still, there is also Document and Desktop folder syncing, and the Disk Utility brings back software RAID, which is huge for us.