I hear this argument a lot that it's not production ready but my personal experience does not agree. I use Swift in production for several apps with relatively large codebases that sustain many hundreds of thousands of sessions per day. I would agree that a full clean/rebuild is not as fast as Objective-C and that the incremental build system sometimes seem as though it is compiling more files than you'd like. However, for most part the incremental build system is fine and in daily use it is not a problem. I could never imagine going back to writing objective-C again when I compare the net gains we've realized coding in Swift. The readability and succinctness of the language, as well as catching bugs at compile-time rather than run-time, is a huge benefit. Value-based programming, functional(-ish) programming, and protocol extensions have made my code so much easier to maintain and test, as well.