Not that impressed, I'm an old school Unix guy and this has moved OS X further away from Unix again, at this rate I can see us moving to WinDoze and Powershell/WSL in the future.
A few big things for us, bash has been replaced with zsh - easy to swap at the moment but you can bet it won't be as easy in the future. It's harder to run non=blessed programs than before - even emailed pdfs/docx files send in from others can not be opened unless you turn the security settings off - this is harder/less reliable to do than before. Apple supplied programs have moved to /System/Applications and only user ones are in /Applications now which has broken a lot of our stuff.
Annoying but we're concerned about the future and it getting harder and harder to support in our Linux environment - it really does look that Windows 10 has better Unix support now than Os X which is something v strange to say.