I've actually been going through my iPod trying to figure out what's child appropriate, and what needs to be set not to play when it's on shuffle. I don't choose to purchase censored music, but I wouldn't play NWA for a toddler, even if it was bleeped. The thing that surprised me is how many reasonably innocent songs have swear words sprinkled in (Ben Folds was the worst here), and how much metal was totally clean. non-American power metal (most of it) tends to be pretty safe, so something like Nightwish or Stratovarius would probably be fine, so long as the music's appealing. And yeah, I started with my Black Sabbath cassette in early high school, and it never really went away.