Been using it production for a couple months now, no issues. We have a reasonable number of IO.js powered microservices, we've seen anecdotally better performance for some use cases but regressions in none, however we've seen SIGNIFICANTLY cleaner code (ES6 yay!) and a much simplified build (no transpilation to ES5!).
Was nervous at first, but now I see no reason to use code Node again.
I think it's still entirely possible for Node's new org to pretty much adopt iojs's technical committee nearly as-is. There's still no version conflicts. There's a minor support niggle for some internationalization bits in node 0.12's core, but beyond that, there's still a chance.
My only thought is that when io.js/node reaches a point for an LTS release, that they do a major bump for the LTS, and another for the ongoing dev... so that #.x.x is LTS. instead of ~#.#.x
Personally I would wait but you can certainly use io.js as you do node. I commented elsewhere in this thread about my whys so I won't be annoying and repeat them here but if you want to experiment or need some bleeding edge performance in some of the areas that io.js is faster (the newer V8 isn't faster in all situations) go for it otherwise I'd stick with node for now.
Was nervous at first, but now I see no reason to use code Node again.