Wow, that's crazy how similar they are! I was just reading a thread yesterday where someone was comparing Stern's Aerosmith and Kiss playfield layouts (hell, i think IJ4 is pretty damn similar to both of them too). Pretty much the same deal, though a little less blatant.
I guess at least people who enjoy ACDC pinball but can't stand the music now have an alternative with SW? I don't even get excited about new Stern releases anymore seeing how often they rehash or slightly change a previous design. Metallica was probably the last good one, but I'm sure it'll be rebranded for those who aren't into their music, too.