@couzteau That's what I'm assuming.  The Wix installer's <MajorUpgrade> functionality defaults to disabling downgrading to an older release.  Plus, when I overrode that setting and experimented with allowing the installation of an earlier release, I noticed that the installer got a bit confused and didn't correctly install all the older files.

I'm hopeful that this won't be a problem, especially just as soon as we implement the portable builds -- ie. the ability to provide builds of older releases as .zip files.