There have been lots of posts on Swift performance since the first beta was released but I'm always reluctant to link to them as it still feels too early to compare performance fairly given how young the language is. Certainly performance has improved drastically since those early beta versions but, there are things you can do to write code to be more performance friendly as well. This post covers some techniques to remove dynamism from your code to give a performance boost where needed.
This is beautiful, and the API couldn't be simpler. I think the first place I saw these kind of animations was in the Skype app, but they are becoming more common now and used sparingly they can be very effective.
JSON → Core Data, the eternal struggle of getting remote data synchronised with a local store. This library doesn't get into the networking side of things but does provide a simple way to take received JSON and sync it with your Core Data models.
This is a neat little library by Didier Brun, define some paths and have them automatically recognised. Obviously this isn't going to be suitable for UI in every app but if you're experimenting with more complex gestures than single path swipes you might want to look at this.