ES6

ECMAScript 6 is a coding standard for Javascript that attempts to make improve the readability and organization of work done by programmers.  In general, ES6 Javascript appears much cleaner and is faster to write than standard Javascript. This standard ensures your code is easier to test and maintain than regular javascript as well. Most web browsers, especially Google's Chrome, have already adopted Native support for the ES6 standard and Node will also run it natively. You can use it in Extensions, Apps and even webpages without translating it with a utility.

Advantages

ES6 Javascript is easier to write, easier to test and more maintainable than regular Javascript.  There are a host of testing frameworks and continuous integration utilities that are all designed to help manage a project written in ES6.  In most cases, you don't even need extra utilities to cross-compile or translate ES6 back to Javascript.

Risks

The only real disadvantage you may run into is the need to compile ES6 back into a legacy version of Javascript that works with your particular device or runtime environment.  This can make your deployment more complicated depending on the situation, but once you have an automated process in place, there shouldn't be any additional work required.  In most cases, there isn't any significant disadvantage for using ES6.