Fighting bad design in Apple products one thing at a time.
The blog went down with a Posterous boat and all the recent posts are lost. I am looking into switching to a self-hosted solutions meanwhile. Sorry for the inconvenience.
… download it here instead: support.apple.com/kb/DL1571
Update went fine on my notebook, but on the desktop computer it started to download 4.3 Gb instead. Even after having the update applied Mac App Store wants to download the full Mountain Lion install again. So if you are in the same situation, download an update from Apple directly.