Now, the message has disappeared, and I cannot find it, not any software it might have been connected with. In Gnome 3, go to activities and do a search for "software update" (or find it in your list of applications). I would suggest changing title of this question so that it better matched the question which is being concerned specifically with upgrading from one release to another.
Generally, when going to a new version, I'll generally do a full re-install of the system.
I have found updating packages in place to be quite problematic and the amount of time spent in debugging the problems there are more complex than doing a reinstall.
Just live with this fact and stay up to date as long as the distro stayed around, using As a new version comes out, you'd manually do a fresh install and take care to copy any data and configurations forward to the new system. This tool essentially just collected your setups and the names of the packages you installed and would assist you in applying them to a new installation.
See @Joel Davis' answer for this technique as well.
When I wrote that I meant "rolling release" to mean that you could now roll from one point release of Fedora (say 17) to version 18.