A) you're completely wrong.
B) In addition to music, you can also turn on/off auto download for apps and books
C) just go into the iTunes app on your iOS device and through that you can re-download individual songs to save space if you must.
A) What did I say was wrong?
B) I know this, but I was only specifically talking about music.
C) I understand, but this solution is not very elegant
You did not understand my point. I rotate my library on and off my iPhone: basically 1/4 of the library is removed and replaced every few weeks. I currently do this by adjusting sync settings in itunes on macbook and re-syncing.
How will I be able to do this with JUST the iPhone and iCloud? From the keynote, iCloud was to replace macbook as the "syncing hub"... but there is no solution if you want to drastically adjust your synced songs. I could use your "C) method" and download song by song by song... but you see how painful that would be?