I'm a user of both Nitrous and c9.

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.