Writing a brand new Mac app for myself, using Objective-C instead of Swift. So far it's a breeze. Yes I used Swift for a while, and it sure feels all academic and all, but meh, ObjC gets the job done just fine for me.
I've noticed that my Java-based coworkers often create well-documented interfaces with only a single implementation. They claim to do it for testability, but Mockito can deal with concrete classes as well - I suspect that they secretly enjoy looking at 10 lines of code that describe what a class does :)
My clients still accept ObjC for new projects, and they'd be crazy not to, considering how much the Swift 3 migration has cost early adopters.
Given my current pessimism about Apple technologies, I think I'll just milk my ObjC skills until everyone goes Swift-only and then look for work in a portable programming environment.