Thanks for the link Chris, that was a great (and lengthy!) read.
For those who may be more time-constrained the author of the post describes his first experience with Swift, facilitated by Chris Lattner introducing him to Swift for TensorFlow, and compares the performance of Swift and C for certain numerics tasks.
He also critiques and compares several languages on a variety of aspects, concluding that overall Swift may be the best compromise he has seen between performance and usability.
The major deficiencies he identifies in Swift primarily revolve around its ecosystem. He calls out the Swift Package Manager as woefully insufficient, lambastes the Foundation framework for (among other things) behaving differently on Mac and Linux, and laments the lack of support for interfacing directly with C++.
His ultimate conclusion is, “Overall, the Swift language itself looks to be exactly what we need, but much of the ecosystem needs to be replaced or at least dramatically leveled-up.”