It's not in the official repositories, but that's probably a good thing considering the frequency of updates during the beta period.

The Chrome beta .deb packages add the Chrome repo to your sources list, so updates are handled through the package manager (no unprompted background updating like in Mac/Windows).

I wonder if there will be any issues including it in the repos because of the integration of the Flash plugin. Then again, for a Linux company, Canonical is pretty willing to use proprietary software where practical.

You can also add the Chromium PPA for daily build updates:

https://launchpad.net/~chromium-daily/+archive/ppa

And as mentioned, installing Chrome will auto-install the Google repo for it as well.

http://www.google.com/chrome/eula.html?platform=linux