I'm really happy that Apple open-sourced Swift in this way. However, most of the ~400 pull requests are fixes for single typos. I hope that managing the GitHub issues won't become too much of a burden for the main developers (those with write access to the repository).
The people contributing those fixes are doing so because they want to contribute, and typo fixes are very easy to be certain about that it's an improvement (without a chance of introducing regressions, etc.).
Of course, as the easy-to-fix problems are eliminated, focus will shift to finding more meaningful ways to make improvements, or just using the language which has fewer problems as a result.
How to tell if something is a "real" contributor rather than someone who sends the occasional spelling fix. I imagine recruiters would be interested in some way to easily tell this.
Although I've seen that a lot of the basic Swift types are written in Swift, so that would be an area to improve too - that is, if anyone can spot one.
Is there a task list for the project? I don't see an 'issues' page.