Yes: http://dev.chromium.org/developers/design-documents/aura

Are there any other projects, Google or otherwise, that's using Aura?

No, because it is horribly broken in many situations: On linux, context menus often end up on a different monitor than the window, on windows, Aura can’t render text readable at all, etc.

Still when I upload a file, I get the native file selection box.

Also, the "use system title bar and borders" option (when right-clicking on the topmost bar) feels a bit like a hack, but I guess it is the best solution to get rid of that extra top window decoration space on most OSes.