Announcing TypeScript 2.0 Beta
    let lowerCased = strs!.map(s => s.toLowerCase());

I'm not a big fan of this, it's really starting to change JS semantics. It's not just type annotations anymore + ES6 . It's starting to look like its own language. Some might like that, I do not.They should be a bit more cautious before introducing these features. What if Ecmascript in the future uses ! as an operator for a totally unrelated purpose ? It's like decorators, they are not in the spec, there is no plan yet to officially had them to the spec, yet, Angular2 which is written in Typescript abuse them. What if in 2 years they are introduced in ES2019 with different semantics ? How Typescript is going to handle that too ?