Are you a musician? How do you do it?

myspacemusic.com, thesixtyone.com, tunecore.com, napster.com, rhapsody.com, ilike.com, indabamusic.com, kompoz.com, boomdizzle.com etc. Which is your favorite? Why or why not? Are you able to become a viable and competitive independent artist with these services? What's your greatest obstical as an independent musician?