Kelly Hodgkins writes about the new Mastered for iTunes songs on the iTunes Store:
Apple's trying to differentiate iTunes from its competitors with a new “Mastered for iTunes” section that's filled with high-fidelity, ear-pleasing music. These tracks are processed using a set of guidelines and tools that'll maintain as much of the sound quality of the original, uncompressed file as possible.
I'm curious to see if they sound any different. Assuming they do, another question remains: if someone registers a track on iTunes Match and then redownloads it, do you receive the “Mastered for iTunes” version?