The Microsoft HD Photo plug-ins for Adobe® Photoshop® CS2 and CS3 are out of beta (which expires December 31st) and have been released for both Windows XP and Vista as well as Mac OSX. Both versions are free and available at the Microsoft Download Center.
HD Photo plug-in works with both Photoshop CS2 and CS3 and the files created with either version are fully compatible cross-platform with Windows Vista, Windows Live Photo Gallery and any other applications that support HD Photo. The new format provides higher image quality by utilizing an expanded range of color information per pixel resulting in the capture of a more complete set of data from camera sensors. The resulting images produce richer color and a wide dynamic range.
HD Photo also offers an option for lossless compression and uses a progressive decoding scheme which quickly and efficiently renders only the viewable portion of the image area that's on screen.
For complete details, visit Bill Crow's blog for additional information and links.