Personally, I've found it quite okay. However, IMHO, if you have a commercial project with a deadline, don't take on board additional risk by installing it. A

Personally, I've found it quite okay. However, IMHO, if you have a commercial project with a deadline, don't take on board additional risk by installing it. A lot of "project management" can be thought of as risk management. A risk is something that's hard to judge or unknown - e.g. will this developer finish on time? Is this implementation going to work? Installing a new version of the dev tooling is definitely a risk. Think about it from the POV of risk management. Are there features of 9.x that you need to complete the project? What are the unknown parameters? It might not compile your code correctly? How do you mitigate it? Time? Money? Reverting back to a previous version? Some risks can be mitigated by the developer, some need to be passed upstream to the customer. e.g. "If you want to deploy on iOS11, we need to upgrade Xcode, which has documented issues, we expect this would require x hours to complete and have the following potential issues."