It happened! io.js Version 1.0.1 (Beta stability) released!

As you know, io.js is focused on new versions of the V8 engine, which includes support for the ES6 standard. While in NodeJS you had to use the --harmony flag at startup and other troubles to support new ES6 features, there are 3 groups of innovations in io.js:

• shipping - innovations marked as stable in V8, such as generators, templates, new string methods, etc. All of them are enabled by default and do not require special flags at startup.
• staged - almost complete, but not tested, or not brought to the ES6 standard. These are "use at your own risk" innovations that require the --es_staging (or --harmony) launch flag
• in progress - all other innovations that should be included with an individual flag (for example --harmony_arrow_functions)

Innovations that are included by default:

• Block Scope
  
  • let
  • const
  • functions in blocks (strict mode only)
  
  
• Collections
  
  • Map
  • Weakmap
  • Set
  • Weakset
  
  
• Generators
• Binary and octal literals
• Promises
• New String Methods
• Characters
• String patterns

Innovations available with the --es_staging flag:

• Classes (strict mode only)
• Extended objects
• Symbol.toStringTag (user-defined results of the Object.prototype.toString function)

More detailed (and, incidentally, very extensive) documentation is available at iojs.org/api/all.html .