Without a doubt, Grand Central Dispatch (GCD) is an essential tool when it comes to building a scalable and responsive app. Here's a nice guide to what's new with Swift 3.0.
Even for the experienced Swift developer, dealing with ranges can be a tricky subject. Thanks @olebegemann for providing some advanced examples with Swift 3.0.
Apple developer veteran Matt Gallagher takes us on a guided tour of his existing Swift 3.0 essays, now updated for the GM Seed. A must-read if you're interested in some expert analysis.
By now, many of us have really seen how Swift 3.0 will impact our existing Swift 2.2 projects. In case you've missed anything, here's another article that highlights the latest control structures, documents and naming conventions.