The only file you can really do anything with is a .deb—that's a Debian-based Linux installer package—meaning that Debian (and Ubuntu) users can install it with a few clicks. Note: On Ubuntu 9 I got a dependency issue when I tried to install, but it was easy to fix: I just enabled the Universe and Multiverse repositories in Synaptic, and upgraded the library it told me too.
As for the browser itself, it's not unlike regular Chrome, barring a few telling differences. For one, the clock is on display in the titlebar, as if this browser is going to be the only app you see when using Chrome OS. There's also a frustratingly enigmatic little Google logo in the top left corner, which looks like a menu. When you click it, it pops up with a prompt to log in with an @google.com email address. Oh well. In any case, downloads are still working from here; feel free to post more mirrors in the comments. [Living in a Google World via Techcrunch]