Windows Vista and .NET Framework 3.0 programmers can access the HD Photo codec from managed code.  There are a few restrictions when using the managed code interfaces compared to the unmanaged WIC interfaces.  Most notably, not all the pixel formats are supported through managed code in this first release, so these pixel formats can't be used with HD Photo.

Documentation on the HD Photo managed code interfaces can be found here:

http://windowssdk.msdn.microsoft.com/en-us/library/system.windows.media.imaging.wmpbitmapdecoder(VS.80).aspx

The managed code interfaces are built into Windows Vista.  For Windows XP or Windows Server 2003, you need to download and install .NET Framework 3.0.

The released version of .NET Framework 3.0 is now available here:

http://www.microsoft.com/downloads/details.aspx?FamilyID=10cc340b-f857-4a14-83f5-25634c3bf043&DisplayLang=en

The SDK for .NET Framework 3.0 is also available:

http://www.microsoft.com/downloads/details.aspx?FamilyId=C2B1E300-F358-4523-B479-F53D234CDCCF&displaylang=en

I'm also working on rounding up some sample applications to demonstrate the use of these interfaces.  I'll start posting these as they become available.