I've used Nitrous when it was called something else (I can't remember what it was) and it was a great idea but the editor felt really slow and odd use.

It couldn't even autocomplete HTML closing tags. That's a major point against it for my use cases.

Another alternative is: https://koding.com/ but they are also really slow. I'm going to give Nitrous another try for my Go development, it may have gotten better.