It's a bit pricey at 40 bucks for 18 songs. None of the songs are master tracks, they are all taken from AC/DC Live (so master in the sense that they are really AC/DC playing, but it's not the album versions). There is a code in the manual where you can download the 18 songs to your hard drive, and play them in Rock Band 2. I'm sure that code can only be used once, so be careful if you buy a used copy.
Nothing from the new album, which is fine, there aren't many songs that I would have removed in favor of something else. There is a live version of "Let there be rock" which I would have dumped, since that song comes on Rock Band 2 anyway.
All that said, I bought it, and love it.