No the DLC is not free, as it turns out. I did buy it however, because I love the game and wanted the new content. There are no new achievements, instead there are challenges you can finish, but they do nothing for your gamerscore.
There's plenty of new boards with new patterns to learn, and playing as Dig Dug and Rally X is pretty cool. Was it worth the $7.99?
Thanks to the great Cpt Slaughter for the VGCE Show Logo!