You must be asking what you have to do with it. If you are a final client, perhaps you won’t notice such difference of an app built in Swift or another programming language. On the other hand, if you are a developer you can now explore all its depths and contribute to it! Swift is kinda fascinating and more intuitive than other languages and similar to others.
Swift makes things simpler, easy to teach and to learn. And that can affect the final user in some way, apps being shipped faster with a better performance.
On my personal experience, the whole saga from the scratch of an app to its publishing date on the App Store lasted about 14 days, including Store’s review process.
For me, this is the natural order of scaling a product and make it more reliable to the developers and customers: Open Source. The advantages of an open source project is the flexibility that allows developers that are not inside the box to solve the issues, because they can show better solutions and the community stands together, hundreds or even thousands of new people inside that code, with more confidence over the language.
But can it spoil the code? Well, that’s why the standards of contributing kick in. Tests must be run to check that changes won’t bring back past issues. There’s is a control.
This is a huge step for Apple that is sometimes criticized for being so closed in its own product world. The first step I’m sure. Soon, we’ll be seeing Swift softwares on Windows, Linux, Android(?), etc. Hopefully you are as anxious as I do.