They're all perfect substitutes. When one is down you can use another. They can't stop us all. I just wish there was a way to automatically redirect to a working instance.
Sadly, the music selection has fallen off a cliff, and the rest is in a sharply downward spiral... in one sense this is because the music industry finally settled on a streaming model that most people are willing to rent, and it's also because the new generation has been brainwashed or trained out of storing their own files.