People are talking here about icloud as it's mostly music. I think the cloud will have little to do with music. Why?
1. The banner Lion + iOS5 + cloud = WWDC makes me think it's on the same level as the 2 OS's. And something that important has to be more than just music.
2. WWDC is not Apple's ipod/music yearly keynote. They have a keynote for the music stuff later in the year. If icloud was mostly music oriented it would not get a WWDC showing. It'd get a showing later in the year at the music keynote.
So me I think icloud will be the glue between iOS and Lion. Knitting them both together. Sure Apple got the music labels involved. But me that's just a side note to the real use of the cloud.
On Monday (Tuesday morning my time) we'll all know for sure.
I'm still convinced all of this music stuff will be the 'one more thing' this keynote, basically introducing a subscription model in iTunes and a music locker to work with iCloud... It's just a thought, but it would be a neat way of explaining the disparity between iCloud itself and the music rumors we keep hearing about.