As I mentioned in my Chromebook notes, one of the weak points for using Chrome OS as a developer is the total lack of good graphical editor. You can install Crouton, which lets you run Vim from the command line or even run a full graphical stack. But there aren't very many good pure text editors that run within Chrome OS proper — most of the ones that do exist are tied to hosted services like Cloud9 or Nitrous. If you just want to write local files without a lot of hassle, you're out of luck.
I don't particularly want to waste what little RAM the Chromebook has running a whole desktop environment just for a notepad, and I'm increasingly convinced that Vim is a practical joke perpetuated by sadists. So I built the Chrome OS editor I wanted to have as a packaged app (just in time!), and posted it up in the store this weekend. It's 100% open source, of course, and contributions are welcome.
Caret is a shell around the Ace code editor, which also powers the editor for Cloud9. I'm extremely impressed with Ace: it's a slick package that provides a lot of must-have features, like syntax highlighting, multiple cursors, and search/replace, while still maintaining typing responsiveness. On top of that base, Caret adds support for tabbed editing, local file support, cloud settings storage, and Sublime-compatible keystrokes.
In fact, Sublime has served as a major inspiration during the development of Caret. In part, this is just because it's the standard for web developers that must be met, but also because it got a lot of things right in very under-appreciated ways. For example, instead of having a settings dialog that adds development complexity, all of Sublime's settings are stored in JSON files and edited through the same window as any other text files — the average Sublime user probably finds this as natural as a graphical interface (if not more so). Caret uses the same concept for its settings, although it saves the files to Chrome's sync service, so all your computers can share your preferences automatically.
The current release of Caret, 0.0.10, is usable enough that I think you could do serious editing with it — I've certainly done professional work with less effective tools, including the initial development on Caret itself — but I'm on a roll adding features and expect to have a lot of improvements made by the end of next week. My first priorities are getting the keybindings into full working condition and adding a command palette, but from that point on it's mostly just polish, bugfixes, and investigating how to get plugin support past Chrome's content security policy. Once I'm at 1.0, I'll also be posting a standalone CRX package that you can use to install Caret without needing a Google account (it'll even auto-update for you).
Working with Chrome's new packaged app support has been rough at times: there are still a lot of missing capabilities, and calling the documentation "patchy" is an insult to quilts everywhere. But I am impressed with what packaged apps can do, not the least of which is the ease of installation: if you have Chrome, you can now pretty much instantly have a professional-grade text editor available, no matter what your operating system of choice. This has always been a strong point for web apps anyway, but Chrome apps combine that with the kinds of features that have typically been reserved for native programs: local file access, real network sockets, or hardware device access. There's a lot of potential there.
If you'd like to help, even something as simple as giving Caret a chance and commenting with your impressions would be great. Filing bugs would be even better. Even if you're not a programmer, having a solid document editor may be something you'd find handy, and together we can make that happen.