Wile I am not sure about this, I suspect that the "one-clicks" might not be working at all right now (maybe because of the cluster move that is still taking place).
I say this because several "one-click" operations seemed to just fail silently during the evening past ... no success emails .. just silence.
Maybe they are queued until the moved cluster is back up? I'm interested myself to see how DH implemented the Joomla 1.5 migration - as it is not as simple as previous "upgrades."
I tried the "one-click" upgrade on one of my test Joomla! 1.3 "one-click" installs several hours ago, and while the Panel reported success, I have not received any email confirming that, and the application has not been updated as of yet.
I'm gonna wait a bit till I know the cluster move is over and any pending batches are likely to be run before I assume is really broken, though.