It is clear that the browser environment imposes some restrictions on what an online IDE can do (restricted hotkeys, no on-machine filesystem access). Notwithstanding that, I've come to prefer the Cloud9IDE environment over local options and love being able to pick-up where I left off as I switch between computers.
There are many things I could do given the time and interest. Learning everything needed to get where I am has taken lots of time that I feel is better spent providing direct value to the product and its users vs. wondering what the 'optimal' dev environment might look like.
I tend to use vi when doing sysadmin sorts of things... but there are a dozen commands that I've relearned several times now, because I learn them, don't need them for a few weeks, and then have to re-learn them when I need them again.
As an alternative, VCS have solved the problem of picking up where I've left off in an IDE-agnostic way so I can use the tools I've grown accustomed to.