Google is known for offering up products to the masses under the "beta" label. For years Gmail was a beta product (it might still be for all we know), and the likes of Google Glass is currently in beta.
With Chrome OS, however, Google allows users to make the choice of whether or not to run a beta version of the operating system. There are three different channels, as Google calls them, which a Chrome OS user can opt into, each following a different update schedule and offering different features.
The Stable channel is the default for Chrome OS, and the most reliable. It's updated every few weeks with bug fixes, and every six weeks or so with feature updates and changes.
Next, the Beta channel is for those who like to work with the latest features even though minor issues are likely. It's updated every six weeks, but receives new features a full month before the Stable channel.
Lastly, the Dev channel is where new features, but also more bugs, can be found; it's updated once or twice per week.
Changing from the Stable channel to either the Beta or Dev channel is a painless process, with the majority of your invested time spent waiting for the update to download.
From the home screen on your Chromebook (or any Chrome OS device), click on your profile icon in the shelf followed by "Settings" in the menu. Along the left side click on the "About" link. Alternately, you can click on the menu button in an open browser window, followed by Settings then About (or Help).
Once there, you'll find details relating to the current channel your Chromebook is using. Click on "More info..." followed by the button labeled "Change Channel."
The most difficult part is deciding which channel you want to move to.
A word of advice: Moving to less stable channels (that is, from Stable to Beta, or Beta to Dev) is possible without losing any information stored on your device. However, going from Dev to Beta (or to Stable) will require you to completely wipe your Chrome OS device. I recommend starting with Beta, then going down to Dev later if you're feeling more adventurous.
After selecting a channel, Chrome will download the update and post a notification when it's done. A simple restart is all that's required to finish the process.
For more information about Google's Chrome OS Beta and Dev channels, read through this support page. Or for more Chromebook how-to content, be sure to check out this page dedicated to all things Chrome OS.