This will take a while, but I'm looking forward to it. It's probably another big step towards "Swift everywhere," without worrying about bridging to C. I've been doing little but Swift since 2014, and really like the language. I'm still "on the fence" about SwiftUI, but that's mostly because of the level of support from Apple, and the [im] maturity of the system. This will help with that.
Also, for the most part, it’s vastly superior to Obj C. The sad thing is that when writing Obj C I often find myself not writing the clean, well structured solution that’s in my head out of sheer resistance to the verbosity that it would take. I always just keep thinking how simple it would be in Swift and how much longer and more keystrokes / files it takes in Objective C.