We are tracking issues with it on the thread below and will post fixes there once they are finalized. We hope to resolve this and add in patches so we can give the All Clear for those who want to update.
http://steamcommunity.com/app/252690/discussions/2/1520386297691959997/
We Caution Mac Users to Hold Off on High Sierra update to OSX for now.
Source: Steam Community (opens in a new tab)