As a datapoint: we build the Minuum Keyboard (http://minuum.com), and our iOS version was written from the ground up in Swift. That is shipped in the App Store and has been since iOS 8 launched.
To echo much of the sentiment here: the language is definitely usable in production now. The tooling is not ready yet. We have wasted untold hours dealing with XCode crashing. If you're contracting this out keep in mind those hours.
There are also some issues with the bridging to Objective-C for Cocoa APIs. As an example: we've had a few cases where for performance reasons we've needed to replace Swift arrays with NSArray objects.
That said: there's a lot to like about the language and there are parts of our codebase that are really nice by virtue of being Swift.
EDIT: I want to agree with a number of people here about using the language your contractor is comfortable with. If you don't have a strong in-house reason to use Swift, Objective-C is going to be around for a long time, so I wouldn't worry about that.
To echo much of the sentiment here: the language is definitely usable in production now. The tooling is not ready yet. We have wasted untold hours dealing with XCode crashing. If you're contracting this out keep in mind those hours.
There are also some issues with the bridging to Objective-C for Cocoa APIs. As an example: we've had a few cases where for performance reasons we've needed to replace Swift arrays with NSArray objects.
That said: there's a lot to like about the language and there are parts of our codebase that are really nice by virtue of being Swift.
EDIT: I want to agree with a number of people here about using the language your contractor is comfortable with. If you don't have a strong in-house reason to use Swift, Objective-C is going to be around for a long time, so I wouldn't worry about that.