The Roadmap [0] has long seen async/await as the defining feature for the TypeScript 2.0 milestone, from what I recall. From what I've read in the blog posts the team wants to prioritize ES6 (ES2015) features first, particularly as async/await is potentially on the standards agenda as early as ES2016 or ES2017...
The surprise in TypeScript 1.6 is that experimental support for async/await is actually included, with the caveats that you have to explicitly opt in to the experimental feature with a compiler flag and that it only works when outputting ES6 code (it fails for ES3 and ES5). Some details are at the bottom of the issue 1664.
Also, I think the new typing capabilities are hugely sexy if you've ever had to write .d.ts files for wild JS. Generic type aliases and intersection types will solve a lot of things that were much harder to do in definition files previously.
Also, the support for expressions in class extends clauses makes it a lot easier to use the nicer class syntax when operating with JS libraries that use a custom object factory. (Given the long history of JS OO, there are a lot of weird custom object factories out there in wild JS code.) This is also good catchup with ES6 class syntax; it's always sexy when TS works to keep its "pure superset" goals.
The surprise in TypeScript 1.6 is that experimental support for async/await is actually included, with the caveats that you have to explicitly opt in to the experimental feature with a compiler flag and that it only works when outputting ES6 code (it fails for ES3 and ES5). Some details are at the bottom of the issue 1664.
Also, I think the new typing capabilities are hugely sexy if you've ever had to write .d.ts files for wild JS. Generic type aliases and intersection types will solve a lot of things that were much harder to do in definition files previously.
Also, the support for expressions in class extends clauses makes it a lot easier to use the nicer class syntax when operating with JS libraries that use a custom object factory. (Given the long history of JS OO, there are a lot of weird custom object factories out there in wild JS code.) This is also good catchup with ES6 class syntax; it's always sexy when TS works to keep its "pure superset" goals.
[0]: https://github.com/Microsoft/TypeScript/wiki/Roadmap