Not enough to say yes in earnest. I help maintain some swift at work, but I put my face in the code base quite rarely. I've not authored anything significant in the language myself. What I have seen is some code where there are multiple different event/mutex/thread models all jumbled up, and I was simultaneously glad to see that was possible in a potentially clean way alongside at least the macos/ios runtime, but the code in question was also a confused mess around it and had a number of fairly serious and real concurrency issues with UB and data races that had gone uncaught and seemingly therefore not pointed out by the compiler or tools. I'd be curious to see a SOTA project with reasonable complexity.