Edit 10/3/2016: We have released SketchUp 2016M2 to address the worst of the issues on Sierra.
Just a reminder that the newly announced (and not yet released) macOS Sierra is not officially supported by SketchUp - if you’re a person who loves to install beta software versions, be aware that SketchUp may exhibit all sorts of unwanted behavior. I ALWAYS recommend installing beta OS versions on separate partitions or removable drives so that you can revert to a known-good OS as necessary.
With that disclaimer, if you run SketchUp on macOS Sierra, we’d love to hear about any issues you encounter.
Edit: Known issues
Crashes/Hangs with text-related tools (labels, text boxes) in LayOut. Bug is related to RTF parsing.