I've just had a ton of issues with the mouse becoming unresponsive... and then having to do a restart, whereas on El Capitan and Yosemite I could basically leave my computer on for forever.
No, I still have not installed Sierra on either. I don't want any siri bullshit. I wonder how long it'll last before I'm somehow forced to upgrade to Sierra. I'm willing to bet it'll be fully baked into the next OS release.