I want to be able to access every single recording of every single piece of music, every film and TV show ever made, every book and article every written in one place.
Ability to download
I want to be able to download a significant amount of this to a local device (smartphone, computer, ebook reader, etc) to cover those periods that I am not connected to a sufficiently fast connection in order to stream.
Service not product
I want to pay-per-use. I expect that the artists I listen to the most will get the most money, and those that listen to it the least get the least money. I want there to be a pricing cap for each piece of music. So, I may pay 0.5c every time I listen, but I pay not more than $1 per track. Once I've spent a dollar on a track I can listen to it for the rest of my life for free. The same should be true for movies: $1.50 every time I watch it, with a $8 cap.
I want a record of everything I've ever listened to, and to be able to search through that data (including through the lyrics of songs). I want recommendations from friends, and recommendations generated based on my ratings of media that I have experienced. I want encyclopedic details of every track, album, artist, etc. I want lyrics to every song. I want to be able to give private and shared reviews of every piece of media I have experienced. I want to be able to highlight and annotate my ebooks.