It doesn't work properly in El Capitan. Due to SIP, it won't install. You can disable SIP and install, but once you re-enable SIP, it works horribly. Leaving SIP disabled is not recommended. (It doesn't run that well on El Capitan even with SIP left disabled.)
What you're left with is the software that opens and can't keep a Wifi or USB connection for longer than half a second. The relay to the phone from the computer is super laggy and slow. Side sync has always been a tad off in speed, but this time it's ridiculous.
Samsung has been notified of the issue, however, their tech support feels it's an Apple issue and not theirs. Who knows if it will ever be corrected.
As with most software things Samsung does, it's half assed, probably will never work as well as it does on Windows and I'm sure they'll drop support for it shortly. As we know from horrible software updates, broken features, all around not the best customer service in regards to supporting the products they make and sell....... I doubt anybody should expect much more from Samsung than that.