You and I, and probably everybody on HN, know what we want though, in terms of the services we use. We're a niche, and actual musicians and artists etc are a niche userbase too, and they wont stop using whatever the hot thing is in their area (soundcloud, let's say). So without sounding too flippant, if Myspace can make the average person think that all the cool people are there, that's where the average person will go, especially if it's as accessible (in terms of the breadth of things it offers) and hip as the preview suggests.
I suppose I just think that not everybody needs, wants or cares about cool. I agree that often the average person will follow the tastemakers, but if you can't keep the tastemakers there, or it's just too out there for the average person (like crazy clothing trends, for instance), you limit yourself to just the fringe.
We may have to agree to disagree :-) It'll be interesting to follow it, though, right?
