Hi mguttman,
You can install the portable version (INI version) of the beta (or any version) side-by-side with the current version.
However, I would recommend you to install the Installer version so that you will not have any issues with the file extension associations or shortcuts. The installer versions run faster than the portable versions. After you use the installer to install the beta version, if you are not satisfied with the new version, you can simply uninstall it, and install an older version. When you uninstall, the uninstaller will ask you whether you want to save your personal settings, and you can select ‘Yes’ to save all your settings. I do this kind of uninstall and install all the time, and there was no problem.
And, please don’t worry about beta. I believe the current latest beta (v11.1.7) is very stable — as stable as the current release version (v11.0.5), and there should be nothing to worry about. Because of a little nice new features available only on the new beta, I would definitely use the new version!
Thanks!