For us it worked quite fine for macOS but not for iOS targets. It also changed the function names for a lot @IBAction functions but did not update the connection in the interface builder. So now I have to a lot of testing to make sure all buttons work.
Still I have to admit it shows quite courage (get it?) to change so many things but naming is important and I see it positively. Only if Apple would use version numbers for Swift that would fit to the state, if you have that kind of fast update cycle and that many breaking changes a version number below 1.0 would have been better for Swift 1 and 2.
