The feature I most miss from other programming languages like Nim is meta programming. In Objective-C you had synthesized properties to generate all the boilerplate code, but in Swift you don't, so to copy certain Objective-C patterns you have to manually write your own private instance variable plus a computed property to control access and side effects. Stuff which is trivially hidden behind a macro. Come on, even Java allows use of annotations to generate code at compile time on Android.
Of course you can argue then that maybe Swift code should not use Objective-C patterns, but hey, I'm still porting and learning. And maybe Swift 2 by the end of the year will have this feature, just like the usage of the where keyword inside conditionals was added recently in 1.2.
I also dislike that there are no forward declarations, so instead of being able to put all your class public API in a single block you have to mingle it with setter/getters' implementations. I guess it's time to use a documentation generation tool and read that instead of reading header files.
The goal of swift seems to nudge programmers further down the immutable, functional path, while still giving them the impression of staying away from the scary FP stuff.