bug 963918 was just 'fix released' even though the implementation was not all the way done. The idea was that one could click on the hud button to close the hud dialogue (much like the BFB closing the dash). However, this does not work when autohide is enabled: the HUD does nothing.
DistroRelease: Ubuntu 12.04
Package: unity 5.12-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
Date: Tue May 8 00:52:07 2012
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
UpgradeStatus: Upgraded to precise on 2012-04-26 (11 days ago)