There is a problem with WSUS wich i think i know the reason of.
When you run updates with automatic reboots and rerun of wsus. If the update is in the WSUSUpdateuser and the computer goes into Standby. and the "show user login after standby" is enabled. then you cant log back into the WSUSUpdateuser. and if you log into the normal one then the wsus user must be deleted manually to continue.
Hope you understand what i mean
And there is another thing. VERY often the updates hang on "Saving registry Hive". i dont know why, but it happens on quite few computers, specially in vista.