All three were previously issued as release candidate versions a month ago, and shared the same list of changes.
Mac users with PowerPC processors receive a fix for an issue with artifacts in highlight areas when processing raw files from Sony, Olympus, Panasonic and various medium format digital camera backs. The problem was introduced in the final Lightroom 2.5 update on the Mac, as an unintended side-effect of the demosaic change made to address sensors with unequal green response in that release.
Both Windows and Mac users also receive new support for Raw files from nine manufacturers - Canon, Leaf, Mamiya, Nikon, Olympus, Panasonic, Pentax, Sigma and Sony - as follows:
Canon EOS-1D Mark IV
Canon EOS 7D
Canon PowerShot G11
Canon PowerShot S90
Leaf Aptus II 5
Mamiya DM22, DM28, DM33, DM56, M18, M22, M31
For more details, visit the Lightroom 2.6 and Camera Raw 5.6, and DNG Converter 5.6 pages on Adobe's website. Note that the Lightroom 3 beta has not been updated with the new camera support at this time. Hence, customers with cameras on the 2.6 upgrade list which aren't supported by Lightroom 3 should use DNG Converter 2.6 to get their images into Lightroom 3 beta.