Microsoft KB934307: Description of the Windows Update Stand-alone Installer (Wusa.exe) and of .msu files in Windows Vista.

Conclusion:
The patch file format .msu for Windows Vista is different from .exe patch files applied to previous OS. The .msu are in fact as same as .cab file formats and could be expanded using expand.exe command.
You can use Wusa.exe(Windows Update Stand-alone Installer) to install .msu patch for Windows Vista.
wusa.exe Windows6.0-KB934307-x86.msu

There’s two important parameters available to wusa.exe:
/quiet /norestart

So it’s possible to implement a automatic patch infrastructure targets to Windows Vista client and server now.