IIS WebAdministration module failing with 80040154

Apart from the normal stuff about the IIS 7 powershell module failing because it's not registered, elevated or you've not allowed the execution of scripts in your powershell session, there's one more little gotcha:

Get-Website : Retrieving the COM class factory for component with CLSID {688EEEE5-6A7E-422F-B2E1-6AF00DC944A6} failed due to the following error: 80040154.

...which is that the COM objects are only registered for x64 (if on an x64 machine), so if you're running a 32 bit PowerShell prompt (for various reasons related to VS GDR) you'll get the error above :-(

See http://stackoverflow.com/questions/3501001/windows-powershell-snap-in-for-iis-fails-on-32-bit for some unsavory workarounds, or just run as x64 if you want it to actually work :-(