You might have noticed by now that Chromium OS has no obvious way to turn things off. Normally, the only power button Chromium OS listens for activity from is the power button of the device it's running on. If you're using VirtualBox, though, you can use the "ACPI Shutdown" command to tell the system to turn off cleanly. A third way, which works in all the environments I tried, is to issue the console command sudo shutdown -P now. (The admin password is required.)
After The First Peek
Now that we've had our first good long look and the initial excitement has died down a little, what's really important about Chrome OS, and Chromium OS?
The first thing that's clear is how Google is forcibly distinguishing Chrome OS from a conventional desktop operating system, for better or worse. This is not and probably never will be a replacement for a desktop, but an adjunct -- in the same way that, for instance, that the iPhone is not a replacement for a full-blown Mac desktop, but a complement to it. (Chrome OS is only meant to run on Google-approved devices, so the parallel to the iPhone has more than one dimension.)
Since the vast majority of computer users do at least some degree of their computing in the context of the Web, most stand to get something useful out of Chrome OS. They may not even have to make that deep a commitment to it for Chrome OS to be successful on its own terms.
Another thing that is immediately clear is how Chrome OS and Chromium OS will exist side-by-side, and thrive on each other's development. The former will be a product, sporting polish (and branding) provided by Google and its associated hardware partners. (And, from the look of it, some software partners as well -- e.g., Canonical.) The latter will be a project, a common baseline from which the finished work is derived -- but also a pool from which could be made any number of derivative works or "re-spins."