None of these systems truly replicates the experience and flow of using VIM for me, but Nitrous seemed like the one that got closest for me to a really solid dev environment/ide on the web with minimum hassle.
I haven't used Cloud 9 in a long time, so maybe this update makes it better.
What I love about Nitrous.io is the speed of their console and the power that seems to be allocated to each box.
What I really don't like is the editor component that they use which likes to interfere with my coding style. When I ask it to indent certain lines it seems to take that as a license to make its own decisions as to what the appropriate tab stop should be.
Recent versions of CodeMirror have improved this a lot, but I remain a much bigger fan of the ACE (http://ace.c9.io/#nav=about) editor component used by (and open-sourced) the c9 team.
I've used these cloud IDEs, but haven't like any of the text editors they supply. Zed is amazing compliment to these services.
But before I toot their horns too loud, they are sort of competitors of mine as the creator of Plunker. Anyway, the more the merrier as long as well all get along and move the experience forward!