When people ask me what I think of the swift programming language, the main thing I think of is hope.
For so long, Apple has been on a kind of island in regards to advances in programming languages. It's the nature of something closed to re-enforce it's own tendencies and design choices. That's why Objective C, a language super-imposed on top of C, with a huge collection of useful (cocoa/touch) libraries based on underlying C libraries (Foundation) has survived and continued to thrive. It's because people had no other reasonable choice for an officially supported, endorsed, widely accepted, fully compatible, method of developing apps on the platform.
You can pick apart swift for what it does well and what it does not, but on the whole it is an advancement that will increase the productivity of iOS developers.
Curiously, one of the biggest advancements we've seen in swift is not even part of the language itself. It's that it is a moving target ever since being released in iOS 8 beta 1. This is a double edged sword. Any developer who has been bitten by building something on top of a moving target (changing requirements/bugs in new apis/etc) can appreciate the reasons to wait for the dust to settle. Early adopters are often penalized in their investment of time. Yet, the fact that it is a moving target re-enforces my hope for it in so many ways.
I've been playing around with swift in a small standalone project just to get familiar and already changes between iOS 8 SDK beta releases have been addressing my concerns. Let me lay out why this is so impressive for the uninitiated. In the past, I waited a year between iOS SDK releases to see pain points I experienced using API's addressed in subsequent releases. Now, in a matter of weeks, between betas, I am seeing improvements to things that matter to me. This language is advancing on a week-to-week basis and Apple is showing a renewed interest in communicating more with a larger development community as evidenced by the fact that they recently made xcode betas free to download, and started a swift blog. These types of things would have been un-imaginable at the Apple of five years ago. Whether the market and their future success as a company requires this or it is just a sea change in attitudes, I think I can speak for a many iOS developers and say "We'll take it!"
I'm excited to see where this swift rocket train goes because rarely do you get to see a programming language evolve this quickly. I'm hopeful that based on what we've seen already, it's going to end up in a really good place.