@SOFI Not sure what Pandora really is in terms of features so i will check that out shortly.
On Spotify, you can buy music and add it to your playlist like iTunes. what i believe really separates this from iTunes and takes it much further is the range of music that can be streamed for free. also friends can be added and faebook/twitter profiles linked (if you use those)... because i think adding friends and seeing their music is a great way to share legally and hear/be introduced to new music.
if only spotify could be used on mobile phones without having to pay for premium membership.
im more of a download and store the file, type of person because i hate when things become unavailable.
but yea, Spotify is definitely worth checking out.