I am running macOS 10.12.1 Developer Beta on one partition where I do most of my work. So when I want to submit iOS apps to the App Store, I switch to a partition running El Capitan so the builds will not be produced with beta software. That's a bit of downside to helping Apple troubleshoot thier new OS. I'm not complaining (much) but it would be nice, now that there is a release version of Sierra, to be able to build iOS apps using it.
Chris