Here's how it went. I tried to remain in the position of a newcomer that has no clue about what a command line interface is, so even if I used a terminal a couple of times, it was just to check some stuff, not to fix it. I launched the mdkonline applet for the purpose of the upgrade (I always disable it because of it wastes too much memory to my taste).

Migration appletOnce launched, a notification popup appeared telling me there was a new distro available. If I record well, I clicked on the applet (and not on the popup), and was a bit surprised to be shown 2008.1 updates. I did those and waited a bit more. I was once again presented with the "new distro available" notification popup. I clicked again on the applet, and was presented the distro upgrade dialog.

Here came the first problem : a curl error, because a package could not be downloaded.

More here