Pandora has the best auto-track selection, but that should be expected, it's their core service.
Spotify is nice in that I can upload and sync my local library, but I have to pay a premium to stream to my iphone. No deal, Spotify.
Grooveshark is great, although their auto-track selection in Radio Mode can't compare to Pandora. Downside, App store won't let me Groove on my iphone.
Finally, iTunes would swoop in FTW if it weren't for all the DRM BS. I can't even migrate my music to another laptop without a 3 hour iTunes fight. Plus, syncing takes forever. Apple needs to step up their cloud music game.
Also, it doesn't allow me to access cloud copies of music, only my own library. Honestly, the concept of an "own library" is obsolete. I want a service that lets me stream anything I want (like grooveshark), with a powerful and intuitive interface (like old iTunes), and a "local library" feature (like Spotify) of anything I want for offline listening. Add in a worthwhile adaptive radio feature (like Pandora) with sharing capabilities (like last.fm) and you've got the whole package.
I don't really organize music because I don't have time for it. But I do have an old iTunes collection that needs organizing and there is no proper tool out there to clean the collection up automatically. I tried tuneup but it doesn't really work well and the software is not very robust or fast.
Regarding creating music - I'd love to see more comments about that here - most of the above comments are about listening to music :-) what about music creation?
Personally i grew up playing the piano but then dropped it after years of suffering and starting using hardware and software for semi-pro music production .. and eventually became a developer of hardware/software for music making :-)
I am very happy with how easy it is to use and don't think about using anything else to listen to music. The only thing I think it needs improvement in is discovery. I have listened to the same tracks probably 100 times each at least. I don't know how/where to find more good music, nor do I have the time to spend a lot of time researching and finding.
To listen to my finds I use spotify, youtube and blogspots and if I can I tend to buy the stuff I like on vinyl/CD.
of interest (php only so far): http://cashmusic.org/ "builds open source digital tools for musicians and labels"
I'm satisfied with a big exception: Rhapsody has lost my music library a few times. That's pretty unforgivable.