I think many people have a concern with CloudKit that once data is in there, they are making a pretty serious commitment to it. Not only is data difficult to extract from it but also you are certainly going to be out of luck if you want to look even slightly away from the Mac and iOS platforms. No web apps, certainly no Android. Tim Schmitz has some food for thought if you're considering using CloudKit.
Chris Eidhof with a very clear and readable post on Tuples, Structs and Enums in Swift. On the same subject, Apple also wrote this article on their official blog, and included a great documentation playground along with it.
Alberto De Bortoli experimenting with flow controllers. The basic idea is that a view controller shouldn't present another view controller, instead leaving that job to the flow controller who's only job is presentation. It's an interesting idea and certainly worth a read.