I'd say it's ready, but it's a bit iffy because of the tooling. The compiler is way too easy to crash, the debugger is often worse than useless, and larger projects can be extremely slow to build.
You can put up with these, and I think it's worth the tradeoff, but you should definitely consider them carefully before putting a lot of effort into build a real-world Swift code base.
Unfortunately, the rise of frameworks has led to another, often ignored problem: app startup time. Carthage and CocoaPods, while great tools, became enablers and I'm hoping static library support will be announced this WWDC.
You can put up with these, and I think it's worth the tradeoff, but you should definitely consider them carefully before putting a lot of effort into build a real-world Swift code base.