New iTunes Match option
The only UI change I have seen so far is in the Setting app, under Music. In 5.0.1, it only allowed you to turn on or off iTunes Match, and allowed you to select whether or not to "Show All Music". In 5.1, they added the ability to turn on/off "Use Cellular Data".
This probably came after a whole bunch of people got dinged for transferring 8GB or more of music using a 2GB data plan. I can only imagine the bill....
By the way, is anybody else out there frustrated that you can't turn on/off "Show All Music" from within the Music app? The use case of "I just remembered, I want that song from iTunes Match" of jump out of the Music App, Go to the Settngs App, turn on "Show All Music", go back to Music, download the song, Go back to settings, turn off "show all music" go back to Music and play. It just seems a little not well thought out.