Comment 3 for bug 1101073

And to clear up a few things:
During quantal I noticed that upgrade option was not offered and I believe I have fixed it. And we had to draw a line somewhere, we do not want to provide "downgrade" option as that is not supported in any sane way. The upgrade is also tricky, as one needs to consider what is considered "current". Thus, the way it's currently implemented "any development release daily image can upgrade/downgrade any development install" (e.g. raring pre-release from day 1 can be "upgraded" using raring from today and vice versa raring install from today can be "downgraded" using raring from day 1) as there is no way to check if the development install is "ahead" or "behind" the booted installation media. In either cases the text to the user will refer to "Upgrading"

But for the final released 13.04 image and installs of 13.04, it should not offer any "upgrade" options. 13.04 released final image should only offer upgrades for 12.10 installations and older.

At the moment this is the desired design and expectation.