Although on Android it's been possible to install different releases of Chrome simultaneously to compare versions and test things out on t, the same thing hasn't been true on Windows and Mac. Once you installed Chrome, it defaulted to the stable channel and you could go into settings to switch to the Beta or Dev channel, but you couldn't have both or all 3 side-by-side. That made it difficult for devs to test their sites or web apps on new versions of Chrome while still being able to monitor their status on the current stable release. (I haven't looked into it, there might have been workarounds, but there was no official solution). But that's changing now.
Starting with Windows computers, users will be able to install multiple channels of Chrome on the same machine and run them in parallel with separate user data directories. All you need to do is head over to the Chrome Release Channels page and grab the installation files for Windows (32 or 64-bit). If you're on the stable channel, you can keep your main installation and grab the Beta and Dev additionally. However, if you were already on the Beta or Dev, you'll need to uninstall them (or presumably revert that installation to stable) then get the files manually from that page.
The Chromium team says that side-by-side Chrome installations are now possible on Windows, Linux, and Android, but will be coming to other platforms soon as well. I'm crossing my fingers for Mac and maybe, just maybe, a potential way to do it on Chrome OS.
- Chromium Blog